The Transportation Security Administration is sending agents to the homes of bloggers, intimidating them into revealing their sources for a leak of the TSA’s enhanced security procedures following the failed Christmas Day terror attack.

Two days later, agents for the TSA, a division of the Department of Homeland Security, visited both men at home, and issued them subpoenas.

“Security Directives are not for public disclosure,” a TSA spokesman said in a statement to TPMmuckraker. “TSA’s Office of Inspections is currently investigating how the recent Security Directives were acquired and published by parties who should not have been privy to this information.”

(Travel journalist and blogger Chris) Elliott posted the subpoena he received on his blog. It demands, under penalty of imprisonment, “[a]ll documents, emails, and/or faxsimile transmissions (sic) in your control possession or control concerning your receipt of TSA Security Directive 1544-09-06 dated December 25, 2009.”

Elliott, according to the subpoena, could face up to a year in jail if he does not comply.

The other blogger, Steven Frischling, who writes for KLM Royal Dutch Airlines, told Wired Magazine about the incident.

Frischling, a freelance travel writer and photographer in Connecticut who writes a blog for the KLM Royal Dutch Airlines, said the two agents who visited him arrived around 7 p.m. Tuesday, were armed and threatened him with a criminal search warrant if he didn’t provide the name of his source. They also threatened to get him fired from his KLM job and indicated they could get him designated a security risk, which would make it difficult for him to travel and do his job.

“They were indicating there would be significant ramifications if I didn’t cooperate,” said Frischling, who was home alone with his three children when the agents arrived. “It’s not hard to intimidate someone when they’re holding a 3-year-old [child] in their hands. My wife works at night. I go to jail, and my kids are here with nobody.”

“They came to the door and immediately were asking, ‘Who gave you this document?, Why did you publish the document?’ and ‘I don’t think you know how much trouble you’re in.’ It was very much a hardball tactic,” he says.

When they pulled a subpoena from their briefcase and told him he was legally required to provide the information they requested, he said he needed to contact a lawyer. The agents said they’d sit outside his house until he gave them the information they wanted.

The case really shows how bloggers are at risk because of the lack of a journalist shield law extending to them. Frischling got the document through an anonymous tip from a Gmail account, and his lawyer told him that he might as well give up the source, not only because of his lack of detailed information about it but because “there was no federal shield law to protect him.”

Take a look at this brazen invasion of privacy:

The agents searched through Frischling’s BlackBerry and iPhone and questioned him about a number of phone numbers and messages in the devices. One number listed in his phone under “ICEMOM” was a quick dial to his mother, in case of emergency. The agents misunderstood the acronym and became suspicious that it was code for his anonymous source and asked if his source worked for ICE — the U.S. Immigration and Customs Enforcement.

The agents then said they wanted to take an image of his hard drive. Frischling said they had to go to WalMart to buy a hard drive, but when they returned were unable to get it to work. Frischling said the keyboard on his laptop was no longer working after they tried to copy his files. The agents left around 11 p.m. but came back Wednesday morning and, with Frischling’s consent, seized his laptop, which they promised to return after copying the hard drive.

As one federal prosecutor told Wired, “it strikes me that they’re more aggressive with this reporter than with the guy who got on this flight.”

It could be that TSA is simply frazzled in the wake of the failed attack, the vulnerabilities detailed in a September security review, and a recent leak of a screening manual to a public government website. But this conduct seems completely out of bounds. Maybe TSA needs a level-headed Administrator.

The federal shield law may be on the way, but whether it will extend to bloggers remains an open question.