The pay of a federal employee may be garnished for any debt other than alimony or child support through legal process issued by an appropriate authority within any state, territory or possession of the United States.
These garnishment regulations are issued by the Director of the Administrative Office of the U.S. Courts at the direction of the Chief Justice of the United States.
Garnishment Regulations (pdf) (Guide to Judiciary Policy, Vol. 20, Ch. 5)