Obligatory \Ob"li*ga*to*ry\, a. [L. obligatorius: cf.F. obligatoire.]

Binding in law or conscience; imposing duty or obligation; requiring performance or forbearance of some act; -- often followed by on or upon; as, obedience is obligatory on a soldier.

As long as the law is obligatory, so long our obedience is due. --Jer. Taylor.

Source: Webster's Revised Unabridged Dictionary (1913)