I do believe that AR15s are available to the public...ballistic vests...yep...APCs...not sure. If there is a law against owning a certain weapon, and someone has one, then they are no longer an otherwise law abiding citizen. I have seen many posts with the same logic regarding illegal aliens...they are breaking the law, but are otherwise law abiding citizens.
So if your municipality were to adopt Chicago-style gun laws, you apparently would not consider a citizen who owned a handgun as law-abiding, and would arrest him. Is that correct?
While the AR-15 is available to the public in most jurisdictions, the ones the police have are full select-fire arms. New select-fire (full auto capable) firearms have been reserved for military and police only in this country since 1986, Which means that while you can theoretically own the same sort of firepower as the police, none of the developments since 1986 are available to you, and the limited pool of existing arms and parts is under greater demand, causing prices to be nuts. An AK which would be a few hundred dollars anywhere else in the world is worth nearly 10,000 here (legal and transferable).
The irony is that those hell-bent on breaking the law will not be constrained in their firearms acquisitions and may have the bankroll to effect those acquisitions, where a person attempting to live within the letter of the law has far fewer options.
Not only does the price structure favor all but the private citizen, the police are bankrolled by and obtaining equipment purchased by our tax dollars, money extracted from us. If I had the option to spend what I pay in taxes on home defense, my place would make Fort Knox look like a garden gazebo.