Sen. Rand Paul at the U.S. Capitol last year. (Mark Wilson/Getty Images)

Another VIP airport fracas: Sen. Rand Paul, outspoken critic of the TSA, missed his flight Monday after a standoff at the security checkpoint.

The junior senator from Kentucky was stopped by after he set off a body-imaging machine at the Nashville airport. Rand, D.C.-bound for a speech at the March for Life, offered to go through the scanner again — but TSA workers insisted on a pat-down. Paul refused and was escorted out of the security area by local police. He rebooked on a later flight and went though security without incident, reports our colleague Ed O’Keefe.

Just an inconvenience? Ha! Paul’s office quickly tweeted about the run-in; his father’s campaign declared that the TSA “gropes and grabs our children, our seniors, and our loved ones and neighbors with disabilities.”

The airport security pat-down in action. (John Moore/Getty Images)

What set off the scanner in Paul’s case? He says it involved one of his knees — though, no, no metal pins or implants, he swears. On landing at Reagan National Airport, Paul told waiting reporters he doesn’t believe he was personally “picked on” but suspects screeners may manually trigger alarms for random frisking.

Rand says he was briefly detained; TSA officials deny that charge. In a statement, they defended their action: “When an irregularity is found during the TSA screening process, it must be resolved prior to allowing a passenger to proceed to the secure area of the airport.”

For all the fuss, the government-sanctioned caress isn’t likely to go away anytime soon, says George Washington University law professor Orin Kerr. Legal challenges that they violate Fourth Amendment rights have been rejected by most judges. “Courts have been deferential to the claims of government need,” he told us. “They say it’s a policy issue, not a constitutional question.”

Paul told reporters he plans to call for a formal Senate inquiry. His office didn’t return our calls for comment.

Read also: Sen. Rand Paul declines TSA pat-down, is escorted from security checkpoint, 1/23/12

Read earlier: Alec Baldwin and other VIP flight risks, 12/7/11