If the White House gun violence policy announced yesterday had been in effect, would it have changed the outcome of recent mass shootings?
It’s impossible to say for certain, but here’s a look at what it might have meant.

NEWTOWN — A tough assault weapons ban might have blocked the sale of the Bushmaster XM-15 that Adam Lanza’s mother bought legally and which police say he used to kill all his victims in the school. A ban on high-capacity magazines might also have reduced the killing power of the weapons he brought to the school.
AURORA — As with Newtown, a ban on assault weapons and high-capacity magazines might have reduced the killing power that James Holmes brought into the movie theater.
TUCSON — Federal law bars gun sales to anyone who “is an unlawful user of or addicted to any controlled substance.” When Jared Loughner attempted to enlist in the Army, he admitted he was a drug user. That information was never reported to the FBI for inclusion in the background check database, because a Justice Department policy dating from the Clinton administration directed federal agencies not to report information volunteered by drug users, for fear that it would deter drug users from seeking treatment.
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