Ageism:
"prejudice or discrimination on the grounds of a person's age.
"
Discrimination:
"In human social behavior, discrimination is treatment or consideration of, or making a distinction towards, a person based on the group, class, or category to which the person is perceived to belong"
So, by that definition of discrimination, allowing one age group to do something another can, is discrimination.
Ageism, the discrimination of groups due to age.
Seems age laws, are ageism. Best ring the po po.