5 CFR § 734.203 - Participation in nonpartisan activities.
An employee may:
(a) Express his or her opinion privately and publicly on political subjects;
(b) Be politically active in connection with a question which is not specifically identified with a political party, such as a constitutional amendment, referendum, approval of a municipal ordinance or any other question or issue of a similar character;
(c) Participate in the nonpartisan activities of a civic, community, social, labor, or professional organization, or of a similar organization; and
(d) Participate fully in public affairs, except as prohibited by other Federal law, in a manner which does not compromise his or her efficiency or integrity as an employee or the neutrality, efficiency, or integrity of the agency or instrumentality of the United States Government in which he or she is employed.