Notwithstanding any law or regulation to the contrary, youth groups registered with the Secretary shall be admitted to any Maryland State park free of any admission or overnight camping charge. This exemption shall apply only when the group is participating in official activities under adult supervision. For the purpose of this section, “youth group” includes, but is not limited to, boy scouts, girl scouts, 4-H members, and other affiliated groups. The Secretary may restrict admittance under this section when a given park is being used to capacity by the public.