Unequal treatment of a state's residents under the 14th Amendment right to domestic travel only occurs when a law expressly differentiates between residents based on their length or timing of residency.
Absent a violation of the right to travel, the equal protection claim should be assessed under rational basis review.
State's offender registration law is insufficiently punitive to base an ex post facto claim upon it; the stated purpose of the legislature was civil and regulatory. In practice, it's sufficiently different from parole, as the status can't be revoked; its restraints and disabilities aren't sufficiently severe to make the law punitive; residency restrictions do not serve punitive aims, and there is sufficient connection to nonpunitive purposes; and the law is not excessive in relation to its aims.
CONCURRENCE:
The registration law is permissibly retroactive; it imposes obligations beyond those prescribed at the time of the offense.
CONCURRENCE/DISSENT:
Requiring registration of residents who are subject to registration in their prior state of residence puts those residents on unequal terms with residents of their present state who are shielded from registration requirments by a decision of the state's supreme court holding the registration requirment to be sufficiently punitive to trigger ex post facto scrutiny.
A resident of the instant state who then travelled to another state where they were subject to registration requirements would then have to register in the instant state upon their return, burdening the travel right.