A prime example of an ex post facto law is a law that punishes a defendant for conduct that was not criminal at the time it was committed. A recent example occurred in a federal district court in the Virgin Islands involving a convicted sex offender. The offender was convicted before the passage of a new federal law requiring increased reporting requirements for former sex offenders. The federal district court reasoned that applying the new federal registration requirement to a former sex offender whose crime of failing to register occurred prior to the passage of the new law. Thus, the court reasoned that retroactive application of the new federal sex offender law violated the prohibition against ex post facto laws.