5 CFR §551.103

1. (a)Covered. Any employee of an agency who is not specifically excluded by another statute is covered by the Act. This includes any person who is:
   1. (1)Defined as an employee in section 2105 of title 5, United States Code;
   2. (2)A civilian employee appointed under other appropriate authority; or
   3. (3)Suffered or permitted to work by an agency whether or not formally appointed.
2. (b)Not covered. The following persons are not covered by the Act:
   1. (1)A person appointed under appropriate authority without compensation;
   2. (2)A trainee;
   3. (3)A volunteer; or
   4. (4)A member of the Uniformed Services.