Tenants moved into unauthorized garage

[Cat R.]

I have a fourplex where one of the apartments are located on top of a garage. That apartment has a connecting door to that garage that the tenants found a way to get in and hang out in. From what I’m hearing, they even started living in it (I don’t live in the area so I need to get my butt down there this weekend).

I sent them a letter on the 28th of AUG letting them know they aren’t to be occupying that area as it’s my storage and it’s not permitted by the city for occupying and their contract is only for the top unit. I also said that I would be coming in two weeks with contractors to get some work done in that garage and to have their stuff  out. 

My question is, if they aren’t out by the time I get there on Saturday or have stuff there still, what can I do within my and their legal rights? This area in LA county (CA) is rent controlled not sure that makes any difference in this scenario.  Hopefully this tenants husband doesn’t come out acting a fool cause he feels his ghetto a** has some say. 

I want to make sure I go prepared and give them whatever notice or if the police would do anything. My first time with this so any help or insight would be appreciated.