You need an attorney to examine all aspects of the case, including whether the original conviction can be overturned. I do a lot of appeals, but I am located across the state, resulting in higher charges for cases in Kent County. I am certain you can find someone local to do this, or you can go outside the local area if you can afford it.
The registration requirements are not based on anyone's opinion of whether someone is a pedophile (someone with a sexual attraction to children), but rather on whether the person is convicted of a listed sex crime. Failure of the attorney to adequately advise the defendant of the consequences of his guilty plea can provide a good basis to withdraw a plea. If a plea is withdrawn, the charges do not just go away. Instead, the defendant would then have to face trial on the charges, unless the prosecutor decided to drop them.
Case law plainly holds that if a person is still in jail or prison, or on probation or parole, or is still required to register, changes in the registration laws can be applied retroactively to him. Once he completely discharges, with no further registration required, a new registration requirement will not apply to him. Although this is what the case law says, it might be possible to launch a challenge to that case law in court. That would almost surely require you to hire an attorney. They would not give an appointed attorney for such a purpose.
Contact me at 248-399-6930 for a free consultation. You and I do not have an attorney-client relationship formed by our communications on this website. Advice given by me on this website is general advice based on partial information. You should not rely on any advice given without first hiring a lawyer in the area where the case is pending, and providing that lawyer with full information.
Unfortunately it is not realistic to expect to be able to litigate a 15 year old felony conviction. When the reporting statutes are changed they are not legally considered punishment. Therefore, there exist no grounds to challenge the new reporting requirements as ex post facto laws. If he is not eligible for release from reporting requirements I am not aware of any other relief available to him.