You also have to factor in how many LEO's are on the 'forcefully resisting confiscation' side and would either refuse to participate in the confiscation or actively fight it.
All the cops in urban and suburban areas would immediately confiscate. It's a matter of no paycheck or a promotion which do you think they would choose?
Rural areas are a different story, but the a ATF and FBI would gear up with the military to go after citizens here and your locals can't protect you. Remember treaty law superceeds constitution and posse commitatus.