Just my daughter the Baltimore County police officer.
I think I found some enlightening guidelines. Throughout the nhtsa guidelines there are references to enclosed cabs and full body-enclosed cabs. No definition of either: https://www.nhtsa.gov/staticfiles/nti/pdf/811458.pdf
With the pertinent part: "98 The requirement to use a safety helmet does not apply if the motorcycle has three wheels, is powered by an electric motor, has a full body‐enclosed cab or has a seat belt assembly or a child restraint system which must be used when the vehicle is in motion. HI ST § 286‐81(c). Persons Under 7 Years Old: A motorcycle operator shall not carry a child younger than 7 years old on a motorcycle unless such vehicle: (1) has three wheels; (2) is powered by an electric motor; (3) has a full body‐enclosed cab or (4) has a seat belt assembly or a child restraint system which must be used when the vehicle is in motion"
Full body-enclosed cab the M3W certainly is not, but the Maryland autocycle law doesn't use the term full body-enclosed cab. I think it can be ridden without the helmet.
