obligatory

adjective2

1. •
   Imposing obligation, legally, morally, or otherwise; binding; mandatory.

   • […] if he speak the words of an oath in a strange language, thinking they signify something else, or if he spake in his sleep, or deliration, or distraction, it is no oath, and so not obligatory. — 1673
2. •
   Requiring a matter or obligation.