As usual, John Lott is on top of this:
http://dailycaller.com/2015/11/25/does- ... -have-now/
It sure sounds scary.
But Bratton surely knows better. Law enforcement is notified every time that a person on the terror watch list attempts to buy gun. If it raises other flags, that case may be further scrutinized.
Being on the watch list doesn’t mean that you have been arrested, prosecuted, or convicted of a crime. Of over 2,000 people on the watch list that bought guns between February 2004 and December 2014, not a single one has been identified as using a gun in a crime.
It is pretty easy to get on the terrorist watch list even if you haven’t done anything wrong. About 700,000 people were on the watch list last year, and this number has grown dramatically during the Obama administration. In 2014, about 50,000 people were on the “no-fly” list. This is a 10-fold increase since the beginning of 2009.