When a law enforcement officer is presented with a person on or in a property where the person occupying it has no claim to the property under color of title, typically the law enforcement officer is likely to summarily order that person to leave the property and will threaten arrest under trespass laws if the person returns. 

LOL... but you can take It up with Johnthe ugly side of landlording.. its rare that I ever give a deposit back and I mean rare.they yell they cuss they threaten but they also do a bunch of damage.. most of them are just wind bags.now the one's that actually hand the property over and have lived there like responsible adults I give those back.. but most of my mid west stuff they never even ask. 

You must always remember, threatening memos seldom change anything.

That means they owe me a net total of $300.Now they're threatening to sue.

After they check Craigslist to see if they can find a better deal LOL.But, just FYI, if a tenant starts threatening that there are problems and hinting about suing - you should know, that a judge would look favorably on you giving them the option to move if they're not happy.  

Now she's a tenant, and now you're in a position to have to watch her and give her warnings, and threaten to evict?  

They feel threatened because they are facing the real probability of being homeless.  

A few months ago they had a bad tenant and her boyfriend started verbally threatening them over a security deposit deduction.

The have started reacting violently and threaten me with violence when the toilet is plugged up again or the sink started leaking or they brought bugs and want me to solve their problems.

I think three days is allowable in this situation.If the unauthorized tenants remained after doing so, you can get a real estate attorney to write a legal but threatening letter for a three-day notice to quit.