The Hatch Act limits certain political activities of federal employees.

Do you mean the Logan Act?:

Logan Act, legislation enacted by the United States Congress (1799) that forbids private citizens from engaging in unauthorizaed correspondence with foreign governments. As amended, the act reads:Any citizen of the United States, wherever he may be, who, without authority of the United States, directly or indirectly commences or carries on any correspondence or intercourse with any foreign government or any officer or agent thereof, with intent to influence the measures or conduct of any foreign government or of any officer or agent thereof, in relation to any disputes or controversies with the United States, or to defeat the measures of the United States, shall be fined under this title or imprisoned not more than three years, or both.

​​​​​​​​​​​​​​​​​>The Hatch Act, a federal law passed in 1939, limits certain political activities of federal employees, as well as some state, D.C., and local government employees who work in connection with federally funded programs. ​The law’s purposes are to ensure that federal programs are administered in a nonpartisan fashion, to protect federal employees from political coercion in the workplace, and to ensure that federal employees are advanced based on merit and not based on political affiliation.​​​​ ​​

https://osc.gov/Services/pages/hatchact.aspx