Maryland Gov. Martin O’Malley today signed a bill banning the sale of assault weapons, limiting magazines to 10 bullets, requiring handgun purchasers to submit fingerprints and get a license, and creating penalties for people who don’t notify police when their firearms are lost or stolen. The Baltimore Sun reports that gun control advocates are now planning Baltimore-area TV ads to bolster support among Maryland voters, in case of a future referendum or campaigns to oust lawmakers who backed the bill in the General Assembly. This ad buy begs the question: Could Maryland’s anti-gun control community gather enough support to change course …