Christopher J. Noonan appeals the 6-month prison sentence the district court 1 imposed after revoking his supervised release. He was released from custody on January 18, 2008, however, and is not serving a further term of supervised release. Accordingly, the appeal is dismissed and counsel’s motion to withdraw is denied as moot. Cf. Spencer v. Kemna, 523 U.S. 1, 5-7, 18, 118 S.Ct. 978, 140 L.Ed.2d 43 (1998) (habeas challenge to parole revocation became moot upon expiration of sentence).