Sex offender registration is a forced contract with the State. In most cases the defendant has no idea that he must register until he or she is being released from prison.
In most cases the defendant does not have to be arrested because legislature has given the discretionary right to the State Police to arrest or apply administrative rules to extend registration by 10 additional years.
A good lawyer should seek to have charges dropped when their client is in compliance. The law violates pain and penalty of law or disproportionate penalties. There is a lot more to say but that is for another day. Thank you!