49 CFR 33.62: Directives.

(a) A Directive is an official action that requires a person to take or refrain from taking certain actions in accordance with its provisions.

(b) A person must comply with each Directive issued. However, a person may not use or extend a Directive to obtain any items from a supplier, unless expressly authorized to do so in the Directive.

(c) A Priorities Directive takes precedence over all DX-rated orders, DO-rated orders, and unrated orders previously or subsequently received, unless a contrary instruction appears in the Directive.

(d) An Allocations Directive takes precedence over all Priorities Directives, DX-rated orders, DO-rated orders, and unrated orders previously or subsequently received, unless a contrary instruction appears in the Directive.