Is this violating any sort of securities laws?

Beyond that the reasons for that law are important.

There are probably State laws that apply as well as local ordinances in some cities.Although I'm not 100% sure, I THINK a landlord is required to keep the rental "habitable" which I think includes things like hot water and a heating system but not things like lawn care or air conditioning. 

@Ismael Reyes my father in law, Gus Lopez.

It’s a good idea for you to also stay educated yourself on the tax laws, but you’ll never be able to grasp it all!

I enjoy working with Summit Law Group on all real estate and corporate matters. https://www.summitlaw.com/

We invest in small condos in specific tenant markets - like college/medical/law students and/or military. 

Even if not required by law, attempt to rent out the unit and mitigate your damages.

Hi,my current accouter is not up-to-date with latest tax laws; I am looking for sharp CPA specializing in Real Estate in Maryland.

So you know they bother me when they happen to me.My thoughts on small claims in your area probably wouldn't be helpful because it's probably different than my area.If I was in your situation, I would document why I kept their deposit and I'd only communicate this via US Mail and I'd do it within the time frame proscribed by law in my area.