What's that again?

Homeland Security Secretary Michael Chertoff said something intriguing in today's USA Today interview. In response to the question, "Have you caught any known or suspected terrorists under the US-VISIT program?," the Secretary replied, "We have sent people back who have connections to terrorism. It's rare you have a card-carrying terrorist because most of the ones we know about are either dead or in jail. But when you see somebody who has links to al-Qaeda, the evidence may not be sufficient to convict them of a crime, but it is sufficient to say this is a person we should be worried about for terrorism. We have certainly sent back people with such links." (emphasis added).

Exactly what "links" to terrorism is the Secretary talking about? Isn't aiding and abetting terrorism a crime? If that's the link he's talking about, why weren't those people detained and tried by our criminal justice system? If he's talking about other kinds of links, shouldn't any link to terrorism be a crime? Shouldn't the last thing for us to do with someone we suspect of being linked to terror be to send that person back to wherever he came from? What assurance do we have that the authorities in whatever country he came from will keep watch over him when he returns?

And, one more thing. I find it hard to believe that most of the terrorists our government knows of are either dead or in jail. It seems to me that USA Today should have asked a follow up question or two.