Whistle-blower or loose cannon?

The Supreme Court will hear arguments Tuesday in a case about a former air marshal, Robert MacLean, who flew undercover and armed to prevent hijackings.

MacLean contends he was fired in 2006 for blowing the whistle years earlier on the Transportation Security Administration for pulling marshals from flights after warning them about a possible hijacking plot.

But TSA, which deploys air marshals, argues that MacLean disclosed secret information and deserved to be fired.

The Supreme Court is expected to decide the case by the end of June.

The main question before the court is whether TSA’s regulations against revealing secrets outweigh a federal whistle-blower protection law aimed at protecting workers who disclose agency actions that represent “a substantial and specific danger to public health or safety.”

The incident that sparked the case came after MacLean was briefed in July 2003 about a “potential plot’ to hijack U.S. airliners.” He then received a text message from the TSA stating that the agency was canceling “all overnight missions.”

MacLean complained to his supervisor and the Department of Homeland Security’s inspector general that the decision wasn’t in the best interest of public safety, but they responded that nothing could be done.

MacLean then tipped off MSNBC, which posted a story about the dispute. After congressional criticism, the TSA dropped its plans.

MacLean was identified as the source for the story years later, after he gave an interview to NBC criticizing the agency’s dress code in a disguise that failed to mask his identity.

He appealed his dismissal to the Merit Systems Protection Board, which ruled that he didn’t deserve whistle-blower protection because his revelation was “specifically prohibited by law.”

But the U.S. Court of Appeals for the Federal Circuit overturned the board’s decision in April 2013 and ordered the personnel board to reconsider his dismissal.

The appeals court acknowledged MacLean had “compromised flight safety” and “could have had catastrophic consequences,” but concluded that his disclosure wasn’t “specifically prohibited by law.”

Solicitor General Donald Verrilli, who represents the government, told the Supreme Court that “sensitive security information” regulations specifically bar disclosure of the number of air marshals, their deployments or missions. Workers could disagree often with how marshals are deployed, but they can’t be allowed to jeopardize transportation by divulging the secrets, the government argued.

“The Federal Circuit’s decision is wrong, dangerous and warrants reversal,” Verrilli wrote.

MacLean served four years in the Air Force and five years as a border patrol agent before becoming an air marshal in 2001. He argued that the order canceling overnight missions wasn’t sensitive security information because the message was sent without that designation and unencrypted to his personal cellphone.

Neal Katyal, a former acting solicitor general who represents MacLean, maintains that the appeals court correctly determined that the department couldn’t retaliate against him for disclosing embarrassing information if he held a reasonable belief that he was identifying a “specific danger to public health and safety.”

“This case shows why Congress created the whistle-blower protections at issue here,” Katyal wrote.

Several groups filed arguments saying the whistle-blower protection law trumps agency regulations about what is secret.

The Office of Special Counsel, an independent agency that protects federal workers from prohibited personnel practices, filed an argument. So did a group of former government officials who served in the FBI, Justice and Defense departments. And six members of Congress joined the case.

“Time and again, agencies have found ways to suppress inconvenient information,” wrote Sens. Charles Grassley, R-Iowa; and Ron Wyden, D-Ore.; and Reps. Darrell Issa, R-Calif.; Elijah Cummings, D-Md.; Blake Farenthold, R-Texas; and Stephen Lynch, D-Mass. “The TSA itself has misused its SSI designation to withhold embarrassing information.”