Agree with tankertrashnav-not a difficult choice when your life or many others are at risk.
Sadly I have been in this position twice as an ops /crew controller-when I had no option but to report my suspicions to my seniors about a crew member (both Captains) reporting for a flight.
Both were subsequently sacked and whilst that aspect is not one I am particularly proud of-I wouldnt hesitate doing again if I had my suspicions.
I am glad to say that both occurences were now over 20 years ago-and it would be nice to think it was a thing of the past-but sadly I somehow doubt it.
Both Captains were extremely likeable individuals which made the choice even more difficult.