Defendant entered an open plea of guilty, without benefit of a plea agreement, for failing to register as a sex offender in violation of the Sex Offender Registration and Notification Act, 18 U.S.C. 2250. The district court judge sentenced him to 18 months in prison, 20 years of supervised released, and a $100 special assessment fee. The Seventh Circuit affirmed. Defendant's plea of guilty to forcible sodomy (Uniform Code of Military Justice, 10 U.S.C. 925), while serving in the Navy, triggered SORNA. The judge's application of a modified categorical approach to examine a limited amount of additional material (the charging instrument) and classify the conviction as a tier one offense was proper.