U.S. Sen. Rand Paul (R.- Ky.) penned a letter to Virginia Gov. Bob McDonnell. But it’s not about his father’s run for president.

Paul, a tea party favorite, is asking McDonnell (R) to sign a bill that would ban state employees — including the Virginia National Guard and State Police — from assisting in the federal detention of U.S. citizens without criminal charges or court hearings.

“It is my sincere hope that you will join me and other freedom-loving Americans in support of HB1160 by signing it into law,” Paul wrote to McDonnell in a letter dated Thursday. “The Father of the Constitution and the architect of the Bill of Rights, Virginia’s own James Madison, would be proud of Virginia’s General Assembly for passing HB1160. ’’

The bill, introduced by Del. Bob Marshall (R-Prince William), who is running for U.S. Senate, was passed in the final days of the legislative session last week by the General Assembly, despite opposition by fellow Republicans.

The legislation is based on the National Defense Authorization Act of 2012, which Marshall and Rand say allows the indefinite government detention of citizens in some cases.

“While the governor does not condone the unlawful detention of U.S. citizens, we do have concerns about the impact, whether intended or not, this legislation would have on Joint Terrorism Task Forces, of which state and local agencies are members, information sharing by and with the Virginia State Police and local law enforcement, and on our Virginia National Guard personnel,’’ McDonnell spokeswoman Taylor Thornley said. “The governor will now review the legislation and determine how best to address those concerns.”