What's TSA's Definition of a Secuity Threat?

The New York Times reported today that the Transportation Security Administration sent a letter to at least four graduate students at MIT informing them that the agency turned down their request for an identification card to work at the nation's ports. The letters noted the students were "security threats."

The students had applied for a so-called Transportation Worker Identification Credential, or TWIC, card, a program the federal government created after 9/11 to tighten security at the nation's ports. The deployment of TWIC has been delayed for months for numerous reasons.

The Times article cites two cases, one involving a German student, the other a British student. In the rejection letters, John Busch, who is identified as a security administration official, wrote, "I have determined that you pose a security threat."