Starting October 1, an adult who is present and directly supervising a minor may not allow the minor to ride a horse unless the minor is wearing a properly secured helmet that meets or exceeds ASTM standards for helmets for equestrian use.
The law applies to riding on public roads or trails, including trails and equestrian facilities in public parks. It also applies to riding at private facilities if the private facility’s primary purpose is to offer recreational, educational, therapeutic, or competitive equestrian activities to the public.
There are exemptions for minors who are crossing a public road that separates land not covered by the law, minors who are engaged in an agricultural practice, minors who are Amish or Mennonite, or minors who are receiving therapy services under certain circumstances.
You can read the new law here: https://mgaleg.maryland.gov/2024RS/chapters_noln/Ch_467_hb0113T.pdf