One way to remember that enforced means "required" or "compelled" is to think of rules being "in force." It's almost always laws, rules, or standards that are enforced — enforced parking regulations, for example, are rules that will earn you a ticket if you don't follow them. The adjective enforced comes from the verb enforce, which originally meant "strive or attempt," and later "compel" or "exert force." The Old French root is enforcier, "strengthen," and also "oppress."