The trustee of an inter vivos trust brought this action in the Probate and Family Court Department for Suffolk County, seeking a declaratory judgment that a child bom out of wedlock to the donor’s granddaughter is “issue” of the donor’s children for purposes of the trust. The nonmarital child remains illegitimate because her paternity has never been acknowledged and her parents have never intermarried.2

The parties named as defendants include all the living beneficiaries of the trust. None has answered, although all have been served with notice. A guardian ad litem (guardian) was appointed to represent the interests of the donor’s minor issue, and he has opposed the relief prayed for by the trustee. A guardian ad litem also was appointed to represent the nonmarital child; he has adopted the arguments advanced by the trustee. The parties signed a statement of agreed facts, and the Probate Court judge granted their joint motion pursuant to Mass. R. Civ. P. 64, 365 Mass. 831 (1974), for reservation and report of the case to the Appeals Court. We granted direct appellate review.

*652The facts agreed are these. On May 7, 1959, the donor established an inter vivos trust that, by its terms, was to be construed according to the laws of the Commonwealth. The trust instrument provided for payment of income to the donor for life, then to her surviving children in equal shares for the duration of their lives, and then to the children’s “issue” by right of representation. The indenture of trust also authorized the trustee “to pay to or for the benefit of the children of the Donor and their issue such amounts of principal as the Trustee . . . may deem necessary for comfort, maintenance, support and education without reduction of the interest of the recipient in income and principal.” The trust is. to terminate twenty-one years after the death of the donor’s last surviving child, whereupon the trustees are to convey the share of each of the donor’s children to that child’s issue by right of representation, notwithstanding prior unequal distributions of principal.

The donor died on August 5, 1969. She was survived by one son and two daughters, one of whom still survives, and nine grandchildren, all of whom survive.3 On July 14, 1973, a unmarried granddaughter of the donor gave birth to a daughter (nonmarital child). The nonmarital child has never been the subject of legitimation, paternity, or adoption proceedings. She has resided with her mother in Vermont, in close proximity to her maternal relatives, who have accepted her as a member of their family circle.

Distributions of principal to the nonmarital child are sought to provide for her support and education. Such distributions were made in the past on joint requests from the child’s mother and grandmother, the trustees then being unaware of the child’s nonmarital status.4 It is undisputed that the nonmarital child is illegitimate, both by the law of this Commonwealth and by the law of Vermont, the State of her birth and the only domicil she has known.

The trustee advances several alternative arguments in support of the declaration he seeks.5 We discuss each in turn.

*6531. The donor’s intent. “It is fundamental that a trust instrument must be construed to give effect to the intention of the donor as ascertained from the language of the whole instrument considered in the light of circumstances known to the donor at the time of its execution.” Groden v. Kelley, 382 Mass. 333, 335 (1981), relying an Dana v. Gring, 374 Mass. 109, 117 (1977), and cases cited. Our review of the trust instrument confirms what is undisputed here, that the instrument itself contains no indication of the donor’s intent to use the word “issue” so as to include or exclude nonmarital descendants. Additionally, assuming that evidence of external family circumstances would be competent, we note that the existence of the nonmarital child was not known to the donor at the time she executed the instrument, the child having been bom after the donor’s death.

In these circumstances, the trustee argues that, absent extrinsic evidence establishing that the donor ascribed a special meaning to the term “issue,” her intent “must have been to use [it] in its usual and customary meaning as generally used, meaning biological issue, regardless of legitimacy, ‘progeny’ or ‘offspring,’” citing Webster’s New Int’l Dictionary (2d ed. 1947). While we take judicial notice that the dictionary meaning of “issue” does not exclude nonmarital children, and it did not at the time the donor executed her indenture of trust, we know of no legal authority for the proposition that contemporaneous dictionary meanings must be read into the ambiguous words of trust instruments. Additionally, the statutory law of this Commonwealth is not wholly consistent with the dictionary definition of “issue” which the trustee urges upon us. General Laws c. 4, § 7, Sixteenth (1984 ed.), provides: “‘Issue’, as applied to the descent of estates, shall include all the lawful lineal descendants of the ancestor.”6 The common law mle is squarely contrary to the tmstee’s position. We have stated that “[t]he word issue . . . must be interpreted against a background *654of statutory phraseology and construction which has remained wholly consistent for well over a century.” Fiduciary Trust Co. v. Miskou, 321 Mass. 615, 635 (1947). Dealing with the question whether an illegitimate child was included within the expression, “the-issue of my deceased children,” we stated further: “We can hardly regard this as an open question in this Commonwealth. It cannot be doubted that by the common law of a few generations ago such words as issue, children, descendants, and so forth as descriptive of a class in a grant, devise, or legacy, in the absence of anything indicating a contrary intent, meant only persons of the class who were bom in lawful wedlock.” Id. at 634. This rule of construction was operative at the time the trust in question was executed, and it concludes the question of the donor’s intent. Because nothing indicates an intent by the donor to include nonmarital issue, precedent requires us to presume that the donor intended, in accordance with the law extant at the time the instrument was executed, to exclude nonmarital descendants from the class denoted by her use of the word “issue.”

2. Equal protection analysis. The trustee argues that application of the mle of construction stated in Mishou, supra, would violate the rights of the nonmarital child to equal protection of the laws as guaranteed by the Fourteenth Amendment to the Constitution of the United States.7 We disagree.

It is the trustee’s contention that the mle of construction as to a donor’s intent discriminates against nonmarital children because, taken in tandem with G. L. c. 190, § 7 (1984 ed.) (see note 2, supra), it impermissibly excludes from trust participation as “issue” all nonmarital children not expressly included unless their parents have intermarried. We do not view this argument as persuasive. The guarantees of the equal protection clause of the Fourteenth Amendment are directed solely to limiting the actions of government. See Commonwealth v. Hood, 389 Mass. 581, 584-586 (1983), and cases cited.

*655The trustee argues, nevertheless, that the rule of construction set forth in Mishou, supra, is subject to scrutiny under the Fourteenth Amendment because the United States Supreme Court has said that “State action . . . refers to exertions of [Sjtate power in all forms.” Shelley v. Kraemer, 334 U.S. 1, 20 (1948). We do not believe that the holding in Shelley is relevant here. “In Shelley, neighboring property owners sought to enforce a private, racially restrictive agreement to prevent the sale of a house by a white seller to a black purchaser. The Court held that judicial enforcement of the agreement constituted State action.” Hood, supra at 588. However, “[t]he Supreme Court has not developed Shelley beyond these facts . . . .” Id.

Shelley is inapposite on its facts. In Shelley, the Court had no doubt that State action was involved because it was clear that “but for the active intervention of the state courts, supported by the full panoply of state power, [the black] petitioners would have been free to occupy the properties in question without restraint.” Shelley, supra at 19. State action was found because judicial enforcement of the “private law” of restrictive covenants effectively barred blacks from participation in a significant segment of the housing market. In Mishou, the court reaffirmed a definition for a word whose meaning, as judicial experience repeatedly showed, would remain ambiguous without judicial clarification. Under the court’s ruling, donors and testators enjoyed freedom to use the word “issue” without explication, confident that we would enforce the instrument containing it to exclude nonmarital children. Similarly, donors have been free to modify the word by stating an additional, contrary intent, in which case we have enforced the instrument to honor that intent. When “issue” is used in a legal instrument, with or without explication, it is the donors and testators who act, not this court nor any other arm of the State.8 Thus, we hold *656that State action is not involved, nor is the equal protection clause of the Fourteenth Amendment implicated, when courts apply rules of construction to wills or trust instruments. Accord Hanson v. Markham, 371 Mass. 262, 265 (1976); Boston Safe Deposit & Trust Co. v. Fleming, 361 Mass. 172, 179 n.7 (1972).9 Therefore, no constitutional rights would be violated if the rule stated in Mishou were to be applied in this case.10

*6573. Obsolescence of the rule of construction. The trastee argues that the Mishou rale should not be applied because it is no longer appropriate to do so in light of current social mores and modem legal developments.11

The Mishou decision was handed down almost forty years ago. In the interim, this court does not appear to have reconsidered the utility or propriety of its rule that, absent clear expressions of a contrary intent, the term “issue” must be read to exclude nonmarital descendants. Indeed, the Mishou court itself did not state the principles underlying this rale of construction; rather, it merely treated the applicability of the rale as a closed question in this jurisdiction. Mishou, supra at 634. Nor was the rationale for the rale subjected to judicial scrutiny in any of the decisions relied upon in Mishou. See Mishou, supra at 634-635, citing Green v. Kelley, 228 Mass. 602, 606 (1917); Sanford v. Marsh, 180 Mass. 210, 211 (1902); Hayden v. Barrett, 172 Mass. 472, 474 (1899); Adams v. Adams, 154 Mass. 290, 292 (1891).

All these decisions treat the rale as sound because it was well settled in English and American law. We must turn to a *658decision written in 1827 for what appears to be the most recent judicial airing of the reasons for the rule:

“[Tjhere seems to be no maxim of [the common] law less questionable than that a bastard is filius nullius .... No doubt the law [barring illegitimates from inheriting as next of kin] was so established on higher principles than the interest of individuals. It was to render odious illicit commerce between the sexes, and to stamp disgrace on the fruits of it; and though the punishment usually falls upon the innocent, yet it was thought wise to prohibit them from tracing their birth to a source which is deemed criminal by law and by religion. It is enough that . . . the authors of this misfortune have the power to repair it by will or by gift; the law will not interpose.” Cooley v. Dewey, 4 Pick. 93, 94 (1827) (Parker, C.J.).

It is questionable whether the attitudes expressed by Chief Justice Parker were representative even of his own era; within two years after Cooley, the Legislature had mitigated the non-marital child’s status as filius nullius by enacting a statute which made such children heirs of their mothers for purposes of intestate succession. See St. 1828, c. 139, codified at G. L. c. 190, § 5 (legislating, as well, a result contrary to the primary holding in Cooley, supra), Monson v. Palmer, 8 Allen 551, 554-555 (1864).

Moreover, while the “source” of nonmarital birth is still deemed criminal in this Commonwealth, see G. L. c. 272, § 14 (1984 ed.) (adultery), and § 18 (1984 ed.) (fornication), “[i]t seems beyond dispute that the statutes defining or punishing [these] crimes . . . have fallen into a very comprehensive desuetude.” Fort v. Fort, 12 Mass. App. Ct. 411, 417 (1981). But see Commonwealth v. Stowell, 389 Mass. 171 (1983) (upholding constitutionality of G. L. c. 272, § 14). In this context, we question the practicality of trying to enforce morality or to preserve traditional family values by rules of con*659struction embedded in the law of trusts. Indeed, the quixotic nature of any such attempt is suggested by the facts that, while the Mishou rule has been in effect, the nationwide number of nonmarital births yearly had risen to 715,200 by 1982, and the rate of such births had more than tripled since 1960. United States Department of Commerce, Statistical Abstract of the United States 62 (106th ed. 1986).

The justice of punishing innocent children for the actions of their parents has long been questioned. Indeed, doubt was expressed in several decisions relied on by the court in Mishou. “Removal of the obstacles to the legitimation of innocent children, who have no responsibility for the circumstances of their birth, and thus ameliorating some of the apparent harshness of the common law, has been the progressive policy of our law as illustrated by statutes and decisions.” Green, supra at 605. See Gritta’s Case, 236 Mass. 204, 207 (1920) (holding nonmarital offspring not “children” within the meaning of the Workmen’s Compensation Act, but “dependents” where they were members of an employee’s family). Acceptance of the idea that justice requires nonpunitive treatment of nonmarital children is reflected in numerous Federal statutes that, over the years before and sineq Mishou, have guaranteed more nearly equal treatment.12 Similarly, although not controlling here,

*660both Federal and State decisions of more recent years give witness to a reconsideration of the harshness of the law’s treat*661ment of illegitimate children. See notes 8, 9, and 11, supra. Finally, we note that our own Legislature recently has declared in another context: “Children bom to parents who are not married to each other shall be entitled to the same rights and protections of the law as all other children. G. L. c. 209C, § 1, inserted by St. 1986, c. 310, § 16.

Thus, if the mle excluding nonmarital children from judicial construction of the word “issue” was not archaic when this court reiterated it in 1947, it has become so. We cannot say that the attitudes underlying that mle, as expressed in Cooley, supra, are so widely held in this Commonwealth today as to warrant our imputation of them to donors and testators who use the word “issue” without explication. Rather, we think that the following sentiment, voiced by the Supreme Court of the United States almost fifteen years ago, comes much nearer to the mark:

“The status of illegitimacy has expressed through the ages society’s condemnation of irresponsible liaisons beyond the bonds of marriage. But visiting this condemnation on the head of an infant is illogical and unjust. Moreover, imposing disabilities on the illegitimate child is contrary to the basic concept of our system that legal burdens should bear some relationship to individual responsibility or wrongdoing. Obviously, no child is responsible for his birth and penalizing the illegitimate child is an ineffectual — as well as an unjust — way of deterring the parent.” (Footnote omitted.) Weber v. Aetna Casualty & Sur. Co., 406 U.S. 164, 175 (1972).

Ours is an era in which logic and compassion have impelled the law toward unburdening children from the stigma and the disadvantages heretofore attendant upon the status of illegitimacy. Consequently, we think it more appropriate henceforth to place the burden of exclusion on those donors who insist on it. Therefore, we overrule so much of Mishou as depends *662upon the traditional rule of construction;13 and we conclude that the word “issue,” absent clear expressions of a contrary intent, must be construed to include all biological descendants.14

A crucial question remains concerning the applicability of the rule we announce today to the parties at bar. “[T]he general rule is in favor of retroactive application of a change in decisional law, . . . [but] [primarily because of concern for litigants and others who have relied on existing precedents, judicial changes in Massachusetts contract and property law have been given only prospective effect.” (Citations omitted.) Payton v. Abbott Labs, 386 Mass. 540, 565 (1982), and cases cited. See also Sullivan v. Burkin, 390 Mass. 864, 870-871 (1984) (statutory interpretation allowing surviving spouse to reach assets placed in inter vivos trust by deceased spouse held to apply only prospectively). The rule stated in Mishou appears to have been controlling in the Commonwealth for 150 years or more. As was said in Sullivan, supra, “The rule of Kerwin v. Donaghy [317 Mass. 559 (1945)] has been adhered to in this Commonwealth for almost forty years .... The Bar has been entitled reasonably to rely on that rule in advising clients. In the area of property law, the retroactive invalidation of an established principle is to be undertaken with great caution.” *663We conclude, then, that the new rule of construction applies only to trust instruments executed after the date of this opinion.15

The case is remanded to the Probate and Family Court for Suffolk County for entry of a declaration that, under the law applicable when the trust instrument was executed, the unexplained word “issue” is presumed to encompass only lawful lineal descendants of the donor.

So ordered.

(concurring in part and dissenting in part, with whom Hennessey, C.J., and Nolan, J., join). I join in the court’s decision to announce the new rule of construction which defines “issue” to include all biological descendants regardless of the marital status of the parents, overruling the rule of construction of Fiduciary Trust Co. v. Mishou, 321 Mass. 615 (1947). I cannot agree, however, with the court’s determination that the new rule not apply in this case.1 There are two compelling reasons to apply the rule announced in a decision to the litigants involved.

First, by merely announcing the new rule without applying it, the court’s action amounts to no more than dictum. Myers v. Drozda, 180 Neb. 183 (1966). Kojis v. Doctors Hosp., 12 Wis. 2d 367, 373-374 (1961). Molitor v. Kaneland Community Unit Dist. No. 302, 18 Ill. 2d 11, 28 (1959), cert. denied, 362 *664U.S. 968 (1960). Note, The Retroactivity of Minnesota Supreme Court Personal Injury Decisions, 6 Wm. Mitchell L. Rev. 179, 184 (1980); Schaefer, The Control of “Sunbursts”: Techniques of Prospective Overruling, 42 N.Y.U.L. Rev. 631, 638 (1967). The court is commenting on an issue which is irrelevant to the disposition of the case. Currie, Suitcase Divorce in the Conflict of Laws: Simons, Rosenstiel, and Borax, 34 U. Chi. L. Rev. 26, 61 (1966).

Second, and more importantly, prospective overruling results in excluding the particular plaintiff and has the potential to remove any incentive to bring challenges to existing precedent because the appellant is deprived of the benefit for the work and expense involved in challenging the old rule, which is admittedly erroneous. See Molitor, supra at 28; Myers, supra at 187; Kojis, supra at 373. To encourage parties in future cases to raise issues which reform and rid the law of antiquated legal doctrines, they should be given the benefit of the new rule. Schaefer, supra.

Courts in other States have applied a new rule or a change in the law to the plaintiff challenging the rule. See, e.g., Nga Li v. Yellow Cab Co., 13 Cal. 3d 804 (1975); Dawson v. Olson, 94 Idaho 636, 639-640 (1972); Barker v. St. Louis County, 340 Mo. 986 (1937); Myers v. Drozda, 180 Neb. 183 (1966).2 Moreover, where the issue has arisen either explicitly or implicitly in the various contexts, from negligence and charitable immunity3 to estate and family law to the property *665rules dealing with the problem of surface water, courts have applied the new rule to the appellant. See In re Marriage of Brown, 15 Cal. 3d 838 (1976) (community property); Nga Li, supra (negligence); Matter of Hoffman, 53 A.D.2d 55 (N.Y. 1976) (wills’ construction); State v. Deetz, 66 Wis. 2d 1 (1974) (common enemy rule of property); Kojis, supra (charitable immunity). Courts apply the new rule to the case at issue, in part because of the public policy consideration of encouraging litigants to initiate challenges which bring about needed changes in the law.4 See Nga Li, supra at 829-380; Molitor, supra; Barker, supra at 1003.

The court’s primary concern in declining to apply the rule announced today to the parties here appears to be the reliance interest of the Bar.51 agree with the court that in the areas of contract and property law “retroactive invalidation of an established principle is to be undertaken with great caution.” Sullivan v. Burkin, 390 Mass. 864, 871 (1984). But, by applying the decision retroactively to the parties before the court, the court does not sacrifice the caution so important in the development of new rules in this area of the law.

The court relies on Sullivan, supra, to conclude that the new rule of construction is not determinative of this case. In Sullivan, *666a widow sought a determination that the assets held in an inter vivos trust were part of her husband’s estate for purposes of establishing her statutory share. The old rule did not permit the surviving spouse to reach assets in an inter vivos trust. It is clear that the husband in Sullivan, through the organization of his affairs and the contents of his will, seemed to be fully aware of this old rule and explicitly sought its protection to prevent his wife from obtaining any of his assets. Therefore, due to the reliance on this old rule, the court denied the widow relief, although the rule was altered prospectively to permit a surviving spouse to reach assets in an inter vivos trust. Id.

Unlike the situation in Sullivan, the intent of this donor in 1959 when she established this trust is far from clear. In fact, it is likely that the donor did not have any “intention at all with respect to the question facing us in this case.”6 Boston Safe Deposit & Trust Co. v. Fleming, 361 Mass. 172, 186 (Braucher, J., dissenting), appeal dismissed, 409 U.S. 813 (1972). Similarly, the New York Appellate Division, in facing an analogous question, noted that it cannot “be said with any degree of assurance that at the time [the testatrix] executed her will she was provided with an explanation of the word ‘issue’ which appeared on the typewritten pages of that document.” Matter of Hoffman, 53 A.D.2d 55, 63 (N.Y. 1976). See Matter of the Estate of Best, 66 N.Y.2d 151, 153 (1985) (accepting Hoffman definition of issue to include legitimate and illegitimate children), cert. denied sub nom. McCollum v. Reid, 475 U.S. 1083 (1986).

Similarly, the Wisconsin court, in carving out an exception to the traditional rule of construction if the illegitimate child is a member of the family circle, noted that once statutes and legal presumption are put aside, there is nothing in the record to indicate that the donor would not have intended to include this particular child.7 In re Trust of Parsons, 56 Wis. 2d 613, *667617 (1973). Because the donor’s intent cannot be discerned from the trust instrument and the court today seeks to “unburden[ ] children from the stigma and the disadvantages heretofore attendant upon the status of illegitimacy,” ante at 661, I would not perpetuate the harshness of the traditional rule of construction to deny this nonmarital child8 participation in the donor’s trust.

By giving relief in this case, the court does not harm the reliance interest of the Bar.9

It is hard to understand why the Bar’s reliance should come before the interests of the child, and the reason articulated by the court does not compel such an unjust result. In fact, the court, by not granting relief in this case removes the incentive of the Bar to change rules which are no longer useful or relevant. The potential negative ramifications which flow from the court’s decision today on the incentive of attorneys to challenge outmoded legal doctrine may be avoided by granting relief in this case. Although the court criticizes the injustice of the law’s treatment of nonmarital children in the past, claiming that “[o]urs is an era in which logic and compassion” dictate that nonmarital children should no longer be stigmatized, ante, it imposes punitive treatment on this particular nonmarital child. The cruel irony of the court’s decision is that not only does this child not receive the benefit of the change she brought about in the law, but, prior to this decision, she was receiving payment from the trust and now, as a result of the decision, she can no longer receive these payments. I respectfully dissent on the failure of the court to apply the new rule to this case.