Is it a law that I must install a brake system to a trailer that I am towing?

The trailer is a car dolly carrying a 2500 lb. car but ONLY the front wheels are elevated. The rear wheels are on the ground.I am towing this with a Cl B RV, Ford 350 Excel. Does the law require that I install a brake system? I know it might be wise but the RV is powerful. If I drive slowly, keep my distance can I get by? The brake system is $600.