Not getting off that easy.
The national guard was sent to N.O. to collect the guns. They took them from every one. No warrant, no backround check. They were acting under orders.
Now, your country's leader orders you to go as a squad in uniform and get those guns. What are you going to do?
You are a local LEO, Sherrif's department, town or state police. Obama orders you to go get those guns. In uniform, official police business, no other warrant or law broken, they just decided and legally voted the law that says you are not allowed to have say a pump shotgun. Now it's your job to go get those shotguns they didn't turn in last week. What are you going to do?
The Federal (and many state laws) wasn't in effect then, so they probably didn't realize that the confiscation was illegal. Now, however, the news about the law forbidding confiscatio has been all over the media sources, so, if they chose to violate the Federal law, they could be held legally responsible for Felony theft of a Firearm. And for violating the laws and the Constitution.
Plus, they would have to live with the local citizens after the fact. There would be hell to pay! One way or another.