Looks like the guns were bought legally.
"...Two handguns recovered have been traced back to Farook. He purchased them legally three or four years ago, an official said. Two rifles were purchased by someone else, possibly a former roommate, also legally three or four years ago. Officials said they don't think that person had anything to do with the shooting.
"These were people that came prepared," Burguan said. "There had to have been some degree of planning that went into this."..."
http://www.cnn.com/2015/12/03/us/syed-farook-tashfeen-malik-mass-shooting-profile/index.html
Even if the "purchase of guns" is made illegal, the bad guys will disregard the laws and get them one way or another.
