It is best to check the specific requirements for each state - there is an on-line summary (just do a search with your favorite search engine).
HOWEVER...while a brake in the towed may not be required by law, it is certainly a VERY good thing to have and use! (One Panic Stop that was successful that could have had a much different result made a true believer (in toad brakes) out of me!!!
(On edit - the '1 & 3/4 ton brick' behind will keep-on pushing at road speed until something (brakes or otherwise) slows it or stops it!!)
There are many different options available - some better than others. FWIW - after much research (several years ago - I'm sure the technology has improved since then) I purchased and installed the Mountain Master system - and moved it from my previous MoHo to my present DP AND later moved it from my previous toad to my present (Saturn Outlook) toad. I have been VERY happy with it.