In Indiana any trailer over 3000# must have brakes with a brake away system capable of applying the brakes for 15 minutes. If it is homemade you simply get a vin# from the BMV and have a one time inspection by a police officer. I see trucks and trailers pulled over on a daily basis getting spot checked. I live near a major highway, gravel pit, recycling center/junk yard, and landscape center so there are lost of trailers traveling my area.
If in violation they usually get a ticket and 7 days to fix it followed up by another inspection. If you fail to fix the problem your trailer is impounded. The trailer shop 3 miles from my house have been busy for the last two years since they cracked down. The owner said they make 10 times the money selling components and fixing broke trailers versus new trailer sales. The local cops seem to love the guys who mow for a living. The trailers are usually poorly maintained and its like shooting fish in a barrel.
Chris