What is a formal decree or proclamation enforceable by law?

A formal decree or proclamation enforceable by law is typically referred to as a "regulation" or "statute." These are authoritative directives issued by a governing body, such as a legislature or executive authority, that establish legal obligations or guidelines. They are designed to govern behavior, ensure compliance with laws, and can be enforced through legal mechanisms. Violations of such decrees may result in penalties or legal consequences.