I. INTRODUCTION

May the Alaska State Commission for Human Rights limit the attendance of third parties at investigative interviews? This question arises in the context of a Commission investigation into a State employee's complaints of workplace discrimination. The Commission issued a subpoena to interview the complainant's supervisor, who refused to be interviewed unless an employer representative was also present. On the Commission's petition, the superior court issued an order to show cause why the supervisor should not be held in contempt. The supervisor moved to vacate the order and dismiss the contempt proceeding; the superior court granted the motion on the ground that the Commission lacked the legal authority to exclude third parties from its investigative interviews. The Commission appeals.

We conclude that the statutory requirement of a confidential investigation, with its specific limits on a respondent's access to investigative materials, clearly authorizes the Commission to exclude third parties from investigative interviews. We therefore reverse the superior court's order dismissing the Commission's petition and remand for further proceedings.

II. FACTS AND PROCEEDINGS

A. Background

1. The Alaska Commission for Human Rights

The Commission for Human Rights is responsible for enforcing Alaska's anti-discrimination laws.1 It will accept a complaint from any "person who is aggrieved by a *960discriminatory practice" prohibited by Title 18, Chapter 80, and its executive director may file a complaint "when a discriminatory practice comes to [her] attention."2 The Commission staff acts on a complaint by first conducting an informal investigation, "promptly and impartially."3 If the investigation shows "that there is substantial evidence of an unlawful discriminatory practice," the Commission attempts to "eliminate or remedy the discriminatory practice through an agreement reached by conference, conciliation, and persuasion."4 If no agreement is reached, the executive director may dismiss the complaint or file an accusation and refer the matter for a hearing before the Commission.5

These investigations are generally confidential by statute. With limited exceptions, the Commission is prohibited from "mak[ing] public the name of a person initiating a complaint or a person alleged to have committed [a discriminatory act or practice] during an investigation."6 "The records of investigation and information obtained by the [C]ommission during an investigation ... are confidential."7 "However, the records and information compiled by the [C]ommission during an investigation shall be available to the complainant or respondent ... at least 10 days before a hearing is held under AS 18.80.120 or upon receipt by the complainant or respondent" of notice that attempts at conciliation have failed, "whichever occurs earlier."8

The Commission's staff is authorized by regulation to use a variety of investigative methods. These include witness interviews, "inspection of documents and premises," and "examination of written submissions of parties and witnesses."9 The executive director may "issue subpoenas, subpoenas duces tecum, and other process to compel the attendance of witnesses and the production of testimony, records, papers, accounts, and documents."10 Petitions to enforce a subpoena may be filed in superior court by the Commission, any individual commissioner, or a Commission employee authorized by the Commission.11

The focus of this appeal is the Commission's unwritten policy, followed for at least 27 years,12 barring third parties from investigative interviews with "certain limited exceptions." As the Commission describes its policy, third parties may be present if the interviewee is "the respondent named in the complaint, or is a member of the respondent's 'control group' management, or has managerial responsibility.' " The Commission also allows witnesses to be accompanied by their own attorneys and, if necessary, an interpreter or a guardian.

2. The investigation

The investigation at issue began when an employee filed two complaints against her employer, the State of Alaska Department of Health and Social Services (DHSS), in August 2014 and February 2015. The Commission opened an investigation headed by investigator Patricia Watts. DHSS responded to the complaints with a letter from Greta Jones,13 an Equal Employment Opportunity (EEO) program manager for the State. Jones's letter identified Dori Lynn Anderson as the complainant's supervisor.

*961When Watts called Anderson to schedule an interview, Anderson responded by email directing Watts to Jones, the EEO manager. Watts replied that she was "within correct procedure to schedule an interview directly with" Anderson and suggested some dates. According to a memorandum drafted by Watts, Jones called a few days later to inform her that Anderson (and another witness whose involvement is not at issue here) had "managerial status that entitled [Jones] to attend the interviews." Watts disputed this: she told Jones that Anderson was "a supervisor but not a high-level manager." Jones also said that DHSS would require a subpoena for the witness interviews, and Watts replied that she would be requesting subpoenas.

Paula Haley, then-executive director of the Commission, issued an administrative subpoena directing Anderson "to appear at the offices of [the Commission] ... to provide testimony" on September 18. On September 14 Jones called Watts "in response to the subpoena" to say that Anderson wanted her to be present at the interview. Watts responded "that the Commission ha[d] to address" whether Jones could attend but agreed to discuss rescheduling. In a letter a few days later Watts confirmed a new date for Anderson's interview, October 6, and informed Jones, "The Commission will not allow anyone else to be present during my interview of Ms. Anderson except for her attorney, if she retains counsel."

Jones and the Attorney General's Office both wrote the Commission, challenging its authority to exclude Jones from Anderson's interview. In a letter to Jones, the Commission's attorney, Stephen Koteff, wrote that the Commission did indeed have the authority to "set reasonable conditions on its interviews of witnesses" and that witnesses "are not entitled to representation ... absent some affirmative right conferred by law." Watts faxed a letter to Anderson the same day, informing her that Jones could not be present at the interview and that the Commission might "seek enforcement of the subpoena in court" if Anderson "refuse[d] to answer or participate in the interview under these circumstances."

3. The interview

On October 6 Jones and Anderson called Watts to initiate the telephone interview. Jones recorded the call.14 Watts told Anderson that "[t]he Commission's statutes require that the Commission's investigations be conducted confidentially. That means third parties may not be present during witness interviews, third parties such as Ms. [Jones]." Watts then asked whether Anderson was ready to "proceed with the interview" without Jones's presence. Anderson replied that she would like Jones present. Watts asked again. Jones interjected that Anderson "is very willing to answer any questions and I'm just here to support her," and Anderson said she felt the same way. Watts asked a third time whether Anderson was willing to be interviewed alone, and Anderson replied, "No." Watts informed Anderson that she risked being found in contempt, and Anderson said she understood. When asked once more if she would be willing to be interviewed without Jones present, Anderson said she "would like support." Watts reiterated that Anderson faced a contempt proceeding and offered her a last chance to answer questions without Jones present. Anderson said, "I don't know how to answer that because I am willing to answer the questions." But she confirmed once more that she would answer questions only with Jones present, and Watts ended the interview.

After the call ended-as Watts described it in a contemporaneous email-Anderson informed Watts that she would be willing to be interviewed alone after all but soon changed her mind, admitting that she had "gone back and forth on having [Jones] there with me when we talk" but that ultimately "I find I do want her there with me." Watts reiterated the Commission's position and asked Anderson to call her if she changed her mind again.

*962B. Proceedings

The Commission filed a petition for a show cause hearing in the superior court. Based on the petition and the accompanying affidavit of investigations director Gay, the superior court issued an order to show cause. Anderson, represented by the Attorney General's Office, filed a motion to vacate the order to show cause and dismiss the contempt proceedings.15 The court held a hearing on June 14, 2016, and, following oral argument, granted Anderson's motion. The superior court issued what it described as a "very narrow" ruling that the Commission did "not [meet] its burden of proof that it ha[d] the authority to require Ms. Anderson to appear for an interview alone in this particular case." In support of its ruling the court noted the lack of a written regulation, inconsistencies in how the Commission explained its policy to Anderson,16 and the absence of any limiting language in the subpoena itself.

The Commission filed this appeal.

III. STANDARD OF REVIEW

"[A] superior court's decision not to hold a party in contempt is committed to the court's discretion and is one to which we will accord considerable deference."17 However, we review questions of law de novo and apply our independent judgment to "adopt the rule of law that is most persuasive in light of precedent, reason, and policy."18 When we review an agency's statutory interpretation in an area beyond its expertise, we use the substitution of judgment standard, applying our independent judgment while "giv[ing] due deliberative weight 'to what the agency has done, especially where the agency interpretation is longstanding.' "19

"Whether an agency action is a 'regulation' requiring rulemaking under the Alaska Administrative Procedure Act is a question of law that does not involve agency expertise," and we review such determinations using our independent judgment.20

IV. DISCUSSION

The Commission's position is that it has the authority to exclude third parties from its investigative interviews and that it has exercised this authority for decades pursuant to an unwritten policy. Anderson counters that an unwritten policy is insufficient and that the Commission's policy has no support in statute or regulation. She also argues that the superior court did not abuse its discretion by vacating the contempt order when the face of the subpoena contained no restrictions on third-party attendance and the Commission's explanations of its policy were inconsistent. We conclude, however, that the confidentiality of the Commission's investigations, mandated by statute, necessarily entails the authority to conduct confidential interviews. We also hold that the subpoena was valid and that it was an abuse of discretion to vacate the order to show cause and dismiss the contempt proceeding.

A. The Confidentiality Of Commission Investigations Necessarily Implies The Authority To Exclude Third Parties From Witness Interviews.

Administrative agencies are created by statute "and therefore must find within the statute the authority for the exercise of *963any power they claim."21 The mandate of AS 18.80.115 -that investigations be confidential-contains by strong implication the authority the Commission needs to limit third-party attendance at investigative interviews. The statute, entitled "Confidential information," provides that "[t]he records of investigation and information obtained by the [C]ommission during an investigation ... are confidential and may not be made available by the [C]ommission for inspection by the public."22 The statute further states that information collected by the Commission "during an investigation shall be available to the complainant or respondent" under two circumstances: (1) ten days before a hearing or after notice that conciliation has failed; or (2) "in accordance with the rules of discovery if an action relating to the charge is commenced in court."23 An implementing regulation states that "[r]ecords of investigation and information obtained during an investigation or inquiry are confidential and may not be disclosed except in accordance with AS 18.80.115."24

Alaska Statute 18.80.115 was added to Title 18 nearly 20 years after the Commission was created.25 The bill proposing the amendment initially contained no provision at all that would give the complainant and the respondent access to the Commission's investigative records. A House committee suggested adding the current language, providing access under limited circumstances,26 and that amendment was adopted.27 The Commission argues that this amendment would have served little purpose if the respondent was meant to have contemporaneous access to the investigation by monitoring witness interviews as they occurred. Whatever the purpose of the amendment, we agree that the current statutory language supports only an intent that the process be confidential as to the respondent as well as to the public at large; the respondent was given access to investigative materials, but only under the circumstances specified in the law.

This construction advances the broad purpose of Title 18, Chapter 80: "the elimination and prevention of discrimination[ ] in many facets of our society."28 "The Commission and its director are charged with broad responsibilities ... to receive and investigate complaints of illegal discrimination."29 To that end, the Commission has a "full panoply of administrative powers, including the authority to investigate complaints."30 In recognizing the importance of the Commission's duty to impartially investigate discrimination complaints, we have noted repeatedly that "the legislature intended to put as many 'teeth' into [AS 18.80] as possible."31

It is reasonable to assume that an investigation that depends on the candor and ease of witnesses in informal interviews would suffer if the Commission could not exclude third parties from those interviews-particularly employer representatives in cases of workplace discrimination. A contrary interpretation could seriously damage the mandate *964of confidentiality: While AS 18.80.115 prohibits the Commission from disclosing investigative material, it imposes no such prohibitions on private parties who have ongoing access to the same material. A witness's candor could be chilled not only because her supervisor is sitting in the chair next to her and listening to every word, but also because the supervisor is free to tell anyone else what the witness tells the interviewer.

Maryland's highest court discussed this issue when it reversed the denial of an injunction excluding the employer from investigative interviews, observing that the employer's presence and demand to have the interviews recorded would "likely have the effect of intimidating or influencing witnesses and frustrating the truth-seeking and confidential nature of the investigative process."32 The court elaborated that "without an unimpeded fact-finding process, the Commission would be precluded from gathering the type of evidence that would normally be necessary to file a ... complaint, and hence, the enforcement authority of the Commission would be inherently limited."33 We agree. Without implying anything negative about the participants' motives in this case, we must recognize that, as a general rule, it is reasonable for the Commission to assume that the presence of third parties at witness interviews would hamper its ability to elicit full and candid statements.

Emphasizing the principle of statutory construction expressio unius est exclusio alterius ,34 Anderson argues that the Commission's investigative powers are limited to what is specifically described in the statute. She contends that other State agencies with subpoena power have been granted specific authority to exclude persons from hearings and other proceedings.35 But Anderson applies the interpretive canon too broadly. When the canon is used to contrast two sets of legislative language, it is usually in the context of two sections of the same statute or closely related statutes, not two completely separate statutory schemes.36 The canon also becomes "less persuasive when applied to two acts passed far apart in time."37 The Commission's duties and procedures, as described in Title 18, Chapter 80, are simply not closely enough related to the statutes governing other executive agencies that we would expect the legislature to have intended them to track each other for interpretive *965purposes.38 Besides, "the maxim should be cautiously applied."39 And where "the legislative purpose can be ascertained with reasonable certainty"-as we believe to be the case here-"the maxims of statutory construction [such as expressio unius est exclusio alterius ] are secondary to the rule that a statute should be construed in light of its purpose."40

Relatedly, Anderson points out that the legislature has expressly authorized other agencies to hold private interviews; it could have done so in Title 18, Chapter 80 but did not. But the agencies Anderson lists are distinguishable. Alaska Statute 42.06.450 provides the Regulatory Commission of Alaska with the authority to "exclude from attendance at the taking of investigative testimony all persons except the person compelled to attend." But the statute creating the Regulatory Commission does not require that its investigations be confidential; in fact, the Regulatory Commission must make records in its possession "open to public inspection at reasonable times."41 An agency that must make its records public may need a specific exception to hold private investigative interviews; an agency charged with keeping its records confidential does not.

Anderson also relies on the fact that both the Office of Victims' Rights and the Office of the Ombudsman may conduct confidential investigations42 but have also been granted specific statutory authority to "hold private hearings."43 But a witness interview during the course of an informal investigation is not a "hearing." At a hearing "there are parties, and issues of law and of fact to be tried, and at the conclusion of the hearing, action is taken which may materially affect the rights of the parties."44 Investigations, on the other hand, "have no parties and are usually held in private."45 "An 'investigation' is nonadversary and contemplates a procedure much less formal and more flexible than applies even to an administrative hearing."46 Whether an agency has explicit authority to "hold private hearings" says nothing about the tools it is allowed to use in its investigations.

Anderson also contends that the Commission's policy of limiting third party attendance at investigative interviews is unlawful unless it is embodied in a regulation. Rulemaking under the Administrative Procedure Act (APA) is required for an agency's "expansive or unforeseeable" interpretations of a statute but not for "obvious, commonsense *966interpretations," because requiring commonsense interpretations to go through the APA's formal notice and comment process "would result in complete ossification of the regulatory state."47 "An agency action may not be a commonsense interpretation of existing law when it adds 'requirements of substance' rather than serving as an 'interpretation of the [statute] according to its own terms.' "48

We conclude that the Commission's longstanding policy of excluding third parties from informal witness interviews is a commonsense interpretation of the statutory requirement that it maintain the confidentiality of its investigative "records and information."49 While the Commission may be well advised to formalize some of its investigative practices through the rulemaking process, it was not required to do so for the policy at issue here.50

B. It Was An Abuse Of Discretion To Vacate The Show Cause Order And Dismiss The Contempt Proceedings.

Anderson argues that even setting aside the question whether the Commission had the authority to exclude third parties from her interview, the superior court did not abuse its discretion when it vacated the show cause order and dismissed the contempt proceeding because Anderson had complied with the plain terms of the subpoena, which said nothing about limitations on attendance. It is undisputed that Anderson appeared telephonically at the agreed time and was prepared to answer Watts's questions, though only on her own conditions: that Jones be allowed to be there too.

Alaska Statute 44.62.590 allows an agency to bring a motion for an order to show cause if it certifies to the superior court that an individual involved in an investigation "(1) disobeys or resists a lawful order; (2) refuses to respond to a subpoena; (3) refuses to take oath or affirmation as a witness; (4) refuses to be examined; or (5) is guilty of misconduct at a hearing or so near the hearing as to obstruct the proceeding." Here, the Commission asked that Anderson be held in contempt for "refusing to obey a subpoena." Once the superior court had jurisdiction,51 it was required to apply the law of civil contempt.52 A party may not be found in civil contempt unless the order at issue was "sufficiently clear" that the responding party should have known what was required in order to comply.53

The superior court appears to have found that Anderson complied with the subpoena because the subpoena required only that she appear for her interview-which she did-while placing no limits on third party attendance. But the subpoena, like most, did not require only that Anderson appear; it *967required her to "appear ... to provide testimony ." (Emphasis added.) A witness cannot satisfy a subpoena by simply showing up and then declining to testify except on conditions she knows are unacceptable to the subpoenaing authority.54

Furthermore, contrary to Anderson's argument, a valid subpoena need not include every detail inherent in the type of proceeding.55 A subpoena to testify at a confidential hearing is not invalid because it fails to note that persons other than the witness may be barred from entering the hearing room; a subpoena to testify at trial is not invalid because it fails to note that the witness might be questioned alone in camera. While Anderson's expressed desire for supportive company at the interview is understandable, it was not reasonable for her to expect that the Commission would accommodate her desire unless it said otherwise on the face of the subpoena. Implicit in subpoenaed testimony is the witness's loss of some control over the circumstances of time, place, and manner. And the record is clear in this case that Jones and Anderson were repeatedly made aware of the Commission's policy of excluding third parties from interviews, even before the subpoena was issued.56

Anderson also relies, however, on the superior court's finding that the Commission's communications about its policy were "clearly inconsistent,"57 arguing that she cannot be faulted for failing to comply with an unclear directive. Watts's September 18 letter to Jones said that no third parties could attend Anderson's interview "except for her attorney, if she retains counsel." The alleged inconsistency appears in Koteff's October 1 letter, in which he informs Jones that "[w]itnesses in such investigations are not entitled to representation, whether by counsel or otherwise, absent some affirmative right conferred by law." But whether Anderson could have an attorney present was immaterial to her compliance; she never indicated any desire to have one. The only issue between the parties was whether she could bring Jones, who according to Anderson herself was not her representative.

Because the Commission had the authority to exclude third parties from its investigative interviews; because it was not necessary that the subpoena explicitly assert this specific aspect of its authority in order to be valid; and because the alleged inconsistency in the Commission's explanation of the policy was immaterial to Anderson's failure to comply, we hold that it was an abuse of discretion to conclude that Anderson complied with the subpoena.

V. CONCLUSION

We REVERSE the order vacating the show cause order and dismissing the Commission's petition and REMAND for further proceedings consistent with this opinion.

Because I would affirm the superior court's order dismissing the contempt proceeding *968against Anderson, I respectfully dissent. Although I share the court's recognition of the important role that the Commission plays in enforcing Alaska's anti-discrimination laws, I cannot agree that a longstanding, unwritten, inconsistently applied policy authorizes the Commission to prevent interview subjects from being accompanied by another person at the interview. Nor can I agree that Anderson failed to comply with a subpoena that "commanded [her] to appear ... to provide testimony" because she appeared with a "support" person.1

As the court explains, the statutes and regulations that govern the Commission's investigations require that it keep confidential the "records ... and information" that it obtains in its investigations.2 The court therefore concludes that there is a "strong implication" that interviews must be confidential and that the Commission has the authority to ban the attendance of third parties. But neither statute nor regulation mandates that each interview involve only the Commission's investigator and the interview subject.3 Nor is there any written authority for the Commission's allowing "certain limited exceptions" to this policy: in addition to attendance by the attorney for an interview subject, third parties can be present if the subject of the interview is also the respondent in the complaint under investigation, or if the interviewee is a member of the respondent's "control group" or has, in the opinion of the Commission, sufficient "managerial responsibility."4 The Commission also did not provide any specific support for its ability to ban third parties before Anderson's interview, stating without further elaboration that it had "ample legal authority" to do so.

The requirement that the Commission maintain confidentiality does not in itself require that it ban third parties from interviews. Other State entities must also maintain confidentiality; the Office of Children's Services (OCS), for example, conducts confidential investigations and gathers and maintains confidential information.5 OCS does not, however, conduct all of its interviews-or even the resulting court proceedings-without the presence of third parties.6 Rather, parties who receive confidential information from OCS are instructed (and in the case of court proceedings, ordered) to maintain the information's confidentiality.7

I also am not persuaded that Anderson failed to comply with the subpoena she received. She did appear as commanded and was willing to provide testimony, as long as her support person was allowed to be present.

Because no statute or regulation establishes that the Commission has the authority to ban third parties from its interviews, and *969because the subpoena did not inform Anderson that she was not permitted to bring a support person to her interview, I would affirm the superior court in this case.