It is difficult to make a case for regulation because the gunman acquired all his guns legally and was not on any law enforcement radar. 

Also, it is difficult to make a case for regulation on the basis that new fully automatic firearms were banned in 1986.

If new fully automatic firearms were banned, then is it not a perversion of the law to sell accessories that make semi-automatics into an automatic.

The supplementary point to this is, what is the legitimate use of an automatic firearm in a civilian application, and does this legitimate use justify the diminishment in public safety from the higher probability of occurrence of incidents like Vegas?