Legal Question in Real Estate Law in California

I don't see any really promising legal options, assuming you mean things like police reports and lawsuits. Tenants smoking marijuana in their own home is not going to stir the police into action; I suppose it's still illegal, but the California police departments have little or no interest in enforcement. The practical solution is to find the air leaks and seal them off (if possible). As far as the circuit breaker goes, if you lost a freezer load of perishables, I suppose you'd have a potential lawsuit for your losses, which would be a consequence of a trespass. A practical solution to the circuit breaker problem might be relocating it, locking it, or something of that sort. Maybe they turned it off by accident, not knowing it controlled your power. I'd certainly discuss both issues with the landlord and see what help you can get there.

The best thing you can do is document it and inform the landlord that you are having problems with his other tenants.