The NRA ad accused the president of being a hypocrite for allowing his daughters to be protected by armed Secret Service agents but not embracing armed guards for schools.
The Republican governor and father of four said at a briefing Thursday in Trenton that the children of public figures should be off-limits to political attacks.
Christie again refused to take a position on Obama's call for a federal assault weapons ban. The governor says he has no influence over what Congress and the president decide.
Christie has said he supports New Jersey's current gun laws. They include an assault weapons ban in place for 21 years.