Thomas Carr is a convicted sex offender who registered as such in Alabama on his release from prison in 2004. In December of that year, he moved to Indiana but did not register with authorities here. He was arrested in 2007 and charged with violating SONRA, the Sex Offender Registration and Notification Act. The problem is that SONRA wasn't passed until 2006, two years after his move. The court didn't get really address whether the arrest was an ex post facto violation, but the 6-3 majority, in an opinion written by Sonia Sotomayor, said Congress did not authorize retroactive enforcement:
“Taking account of SORNA's overall structure, we have little reason to doubt that Congress intended [the statute] to do exactly what it says: to subject to federal prosecution sex offenders who elude SORNA's registration requirements by traveling in interstate commerce,” wrote Justice Sonia Sotomayor in the majority opinion.
Justice Sotomayor said Congress chose to use the present-tense word “travels” in the statute, rather than the past-tense word “traveled.” If Congress wanted the law to apply to travel undertaken before the law's passage, it would have used the past tense, she said.
Journalism students are lectured all the time about the importance of using exactly the right word. This is a great example of how one word changes everything. Justice Samuel Alito complained in dissent that the ruling would aid sex offenders who "avoided" registration programs by "moving from one state to another before SONRA'S enactment." That's like saying I "avoided" prosecution for not wearing a seat belt by not wearing it before there was a law against not wearing it -- how devilishly clever of me! We can appreciate Alito's frustration that this is a good deal for the perverts, but the court is there to interpret what Congress does and whether that is constitutional, not to make rulings based on the outcomes justices want. Mr. Alito is usually found in that camp, not on the other side of it.