D defs.my
Entry 1 sense Webster, 1913

Obligatory

/əb-lĭg'-ət-ôrˌ-ē/ · Ob·li·ga·to·ry · IPA /əˈblɪɡ.ə.tɔ.ɹi/
01 a. Binding in law or conscience; imposing duty or obligation; requiring performance or forbearance of some act; -- often followed by on or upo…
  1. 1.
    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.