Legal Question in Constitutional Law in California

Not that I know of. A 5150 is a civil commitment and not a criminal conviction, so the procedures that can be used to reduce a criminal record don't apply. And in theory it doesn't say you did anything wrong but rather that there was reason to think you might have been a danger to yourself or others.

But a 5150 hold is only for three days, and the resulting ban on gun ownership lasts only for five years. If all you had was a 5150 hold, then you should be able to own a gun now.

If your hold was continued beyond 3 days, then you had a 5250 hold. California law imposes the same five-year ban in 5250 cases, but federal law requires a lifetime ban.

There is a procedure by which you can ask a state court to certify that you can safely own guns again, but that finding will only address the state-law ban -- which should be over by now anyway. It may or may not affect your rights under federal law.