DOT helmet rules are comical. I was a WI state trooper for 25 years and never ever checked a riders helmet for DOT certification. Why?
1.) The US DOT does not even test helmets for safety. They have their standards and it's a On Your Honor system for manufactures to claim that their helmets meet DOT specs.
2.) Euro ECE 22.05/latest 22.06 helmet safety specs exceed DOT safety specs.
3.) The majority of States now, with exceptions, don't require helmets. Here in WI, the exceptions are riders 16-17 and those riders who don't have a M (motorcycle) endorsement. If a qualified rider is wearing either a Euro helmet or novelty helmet that doesn't have DOT qualifications, they can just take it off. No court in WI would ever find a rider guilty of a non DOT helmet if they meet helmet exceptions.
I get that rider safety classes need the helmet requirement. They should be allowed to waive the DOT spec if the helmet meets either Euro 22.05/22.06 specs. Off my soapbox now.