man·da·to·ry 
(măndə-tôr′ē)
(măndə-tôr′ē)adj.
1. Required or commanded by authority; obligatory: Attendance at the meeting is mandatory.
2. Of, having the nature of, or containing a mandate.
3. Holding a League of Nations mandate over a territory.
n. pl. man·da·to·ries
A mandatary.