A helpful reader sends word that Connecticut legislators are considering a bill which would make it a crime for any out-of-state sex offender to enter the state without registering within 48 hours. You may read the proposed law here. From the relevant subsection:
It's likely that this law would raise right to travel issues that have not gained much traction in residency restriction cases.
Any person who is a registered sexual offender under the laws of any other state who enters this state and fails to notify the Commissioner of Public Safety in writing not less than forty-eight hours prior to entering the state of the information required under this section or falsely reports such information shall be guilty of a class D felony.