Compulsory (adjective)

1. That must be done; required.
2. Obligatory; mandatory.

Origin:

Early 17th century: from latin compulsus, past participle of compellere "compel", from com- "together" + pellere "drive".

Examples:

1. Compulsory military service.
2. Compulsory attendance at school.
3. Compulsory voting laws.
4. Compulsory retirement savings plans.
5. Compulsory helmet laws.