In Oct. 2013, Gov. Brown signed SB 530 to among other things create a new section of the California Penal Code 4852.22, which reads:
Except in a case requiring registration pursuant to Section 290, a trial court hearing an application for a certificate of rehabilitation before the applicable period of rehabilitation has elapsed may grant the application if the court, in its discretion, believes relief serves the interests of justice.
Are there any grounds on which the PC 290 exception could be challenged? Does it violate the Equal Protection Under the Law doctrine?
The case law on this is really strong and the answer is no. Registration (cleverly) is not considered punishment, so there is not an equal protection argument. Our courts have deemed registration a regulatory issue, so it does not open up the Pandora's Box that you are suggesting may be proper.
While I am not opposed to 290 registration, and I appreciate its purpose, I also appreciate your question.
I can cite a bunch of cases on this issue, but you can also find them discussed in article on my website. This is a complex area of the law.