Remember US v. Miller?
That court ruled against Miller because it thought a sawed-off shotgun was not a military-type firearm. The implication of that decision is ownership of a military-type firearm is protected by the 2nd Amendment.
Should that current ban on assault weapons get to to the SCOTUS, it'll be a stretch IMHO for them to allow the ban in light of Miller.
I haven't read all the posts on this thread, so if someone else has posted the same opinion as I just did, I apologize for the duplication.
Never argue with a fool; onlookers may not be able to tell the difference.