WASHINGTON (AP) — Sen. Rand Paul of Kentucky, the son of Republican presidential candidate Ron Paul and a frequent critic of the Transportation Security Administration, was stopped by security at the Nashville airport Monday when a scanner set off an alarm and Paul declined to allow a security officer to subsequently pat him down. The White House said airport security acted appropriately.

Police escorted Paul away, but he was allowed to board a later flight. The security scanner identified an issue with the senator’s knee, although Paul said he has no screws or medical hardware around the joint.