Recently in US vs. Fernandes, No. 09-30135 (3-14-11)(Per curiam with Thomas, Graber, and Tallman) the question arose whether a court must order a defendant convicted of abusive sexual contact under 18 USC 2244(b) to register as a sex offender? The defendant here worked as a security officer at a national park when he fondled and groped an intoxicated female employee in her room without her permission. The court sentenced the defendant to probation, but refused to require registration. The court explained/felt that there was no need for registration as the defendant had no priors, and would be unlikely to repeat such an offense. It doesn't matter, explains the 9th, which reverses and amends with instructions to put registration as a condition.
Under the statutes, the defendant was convicted of a sexual offense, he is defined as a sexual offender, and so he must register. There is no discretion afforded. The defendant's arguments about discretion under Booker and parsimony do not trump a congressional mandate. The constitutional challenge is also denied.