Without the benefit of a written plea agreement, Barney D. Watson pleaded *14 guilty to unlawfully possessing a machine gun. The district court 1 declined to depart downward from the Sentencing Guidelines, and sentenced Watson to 18 months imprisonment and 3 years supervised release. On appeal, Watson’s counsel has moved to withdraw, and has filed a brief under Anders v. California, 386 U.S. 738, 87 S.Ct. 1396, 18 L.Ed.2d 493 (1967), suggesting that the district court abused its discretion in denying a departure.

We find that the district court understood its authority to depart, and thus its discretionary decision not to do so is unreviewable. See United States v. Orozco-Rodriguez, 220 F.3d 940, 942 (8th Cir. 2000). We also have carefully reviewed the record in accordance with Penson v. Ohio, 488 U.S. 75, 109 S.Ct. 346, 102 L.Ed.2d 300 (1988), and have found no nonfrivolous issues. Accordingly, we grant counsel’s motion to withdraw, and we affirm.