Compulsory

a.	1.	Having the power of compulsion; constraining.
	2.	Obligatory; enjoined by authority; necessary; due to compulsion. This contribution threatening to fall infinitely short of their hopes, they soon made it compulsory. - Burke.

Adj.

1.

compulsory - required by rule; "in most schools physical education are compulsory"; "attendance is mandatory"; "required reading" Synonyms: mandatory, required

absolute, binding, choiceless, coactive, compelling, compulsatory, compulsive, conclusive, constraining, decisive, decretory, dictated, driving, entailed, exigent, final, hard-and-fast, imperative, imperious, importunate, imposed, inevitable, involuntary, irresistible, irrevocable, mandated, mandatory, must, necessitous, peremptory, prescript, prescriptive, pressing, restraining, ultimate, urgent, without appeal, without choice