5 U.S.C. § 5520: Withholding of city or county income or employment taxes

provides for the collection of a tax by imposing on employers generally the duty of withholding sums from the pay of employees and making returns of the sums to a designated city or county officer, department, or instrumentality; and imposes the duty to withhold generally on the payment of compensation earned within the jurisdiction of the city or county in the case of employees whose regular place of employment is within such jurisdiction; This section does not give the consent of the United States to the application of an ordinance which imposes more burdensome requirements on the United States than on other employers or which subjects the United States or its employees to a penalty or liability because of this section. An agency of the United States may not accept pay from a city or county for services performed in withholding city or county income or employment taxes from the pay of employees of the agency. is classified as a municipality by the Bureau of the Census, or possesses powers and performs functions comparable to those associated with municipalities, is closely settled, and contains within its boundaries no incorporated places, as defined by the Bureau of the Census, “county” means any unit of local general government which is classified as a county by the Bureau of the Census and within the political boundaries of which 500 or more persons are regularly employed by all agencies of the Federal Government; “ordinance” means an ordinance, order, resolution, or similar instrument which is duly adopted and approved by a city or county in accordance with the constitution and statutes of the State in which it is located and which has the force of law within such city or county; and an Executive agency; the judicial branch; and the United States Postal Service.