To clear up some of the generalizations seen on this thread I would like to add a little.
First lets hope he doesn't prove positive, although if they cancelled the flight it seems cut and dried as a breath test would have cleared him quickly.
The fact that he got past the screeners is the same as the America West guys in Miami and that is that they must be seen with the intention of flying before they can be stopped. It is possible for a crew, that are suspected of being over the top, to sit in the cabin, or wait at the gate, and say we havn't been drinking for 8hrs before attempting to get in the front seats. Yes, I know they would catch hell for delaying the flight but they just might get away with the police action.
Another point to remember is that at least two pilots have been accused by the screeners at Dulles in the past few weeks and they proved to be completely sober. One of those was accused 4 hours after he had passed security and had a pissing contest with a screener due to the crew having to go through the passenger line as there were not enough screeners to run the employee line.
These people are employed by the TSA and seem to be untouchable.
Lets hope this case works out OK but I have just heard his name in the TV news and he had been charged so it is not looking good.