Can I be evicted in California for having a guest, a pet, or an extra roommate?

It comes down to what your lease says and whatever local ordinance covers your building, so there's no single universal answer here.

Before anything else, he typically owes you a written notice, and depending on where you live, especially under just-cause rules, meaning rules that require a legally recognized reason for eviction, a genuine opportunity to correct the problem first. Skipping straight to eviction without that step is itself something worth challenging.