FACA identifies four sources of authority for establishing an advisory committee:

(a) Required by statute. By law where the Congress establishes an advisory committee, or specifically directs the President or an agency to establish it (non-discretionary);

(b) Presidential authority. By Executive order of the President or other Presidential directive (non-discretionary);

(c) Authorized by statute. By law where the Congress authorizes, but does not direct the President or an agency to establish it (discretionary); or

(d) Agency authority. By an agency under general authority in title 5 of the United States Code or under other general agency-authorizing statutes (discretionary).