Legal Question in Criminal Law in California

Is it legal to charge you? Yes, if the prosecutors believe you knew the meth was there. Barring some unusual facts, driving a car that you know contains meth would make you guilty of possessing it. That's different from owning it; your comment that it wasn't yours misses this rather important point.

You need a good criminal defense lawyer right away -- especially if you told the police that you knew about the meth. The court will appoint someone for you if you can't afford to hire counsel.

Good luck.

Break this down.

Could they stop you? The registration was expired, giving them a reason to pull you over.

Could they search? If your probation includes a search waiver, then they could search. If it didn't, then there may be an issue as to why they searched.

Can they charge you? A person has to knowingly possess drugs. That depends on the facts - where it was found, what you said, etc.

You need a lawyer.