currently in my State, registration and background checks for Rifles don't exist, they do for Hand Guns.
You must not live in the US then, dealers must perform a background check on all cartridge weapons, only black powder guns and airguns are exempt from that requirement.
I can go down town to a Pawn shop, walk in and walk out with a crippled AK47, come home and order some parts...and have a fully automatic weapon to mow down some folks I'm pissed at.
Well that and don't forget your visit to the machine shop, also don't be surprised when the atf shows up at the same time as your parts. They tend to keep a close watch on parts that can be used to make an automatic weapon. Have them shipped to a name and address not on the list of registered machine guns and they take an interest in it.
I am under firm belief the second amendment pertains to Law enforcement and Military usage.
The second amendment applies to the people and the militia, look it up it uses both of those terms, it doesn't say military or law enforcement in it. Further the guys who came up with the second amendment... said things like
"The right of the people to keep and bear... arms shall not infringed. A well regulated militia, composed of the people, trained to arms, is the best and most natural defense of a free country..." - James Madison, I Annuals of Congress 434 (June 8, 1789).
"I ask, sir, what is the militia? It is the whole people, except for a few public servants." - George Mason, 3 Elliot, Debates at 425-426.
Who are the militia? Are they not ourselves? Is it feared, then, that we shall turn our arms each man against his own bosom? Congress shall have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birthright of an American.... The unlimited power of the sword is not in the hands of either the federal or state governments, but where I trust in God it will ever remain, in the hands of the people." - Tench Coxe
"... the British Parliament was advised, by an artful man to disarm the people that was the best and most effective way to enslave the people - but they should not do it openly; but to weaken them and let them sink gradually, by totally disusing and neglecting the militia." - George Mason, Virginia Ratifying Convention, 1778.
If you look at it they intended for the second amendment to apply to everyone EXCEPT for law enforcement and the military. Law Enforcement officers and military members are not allowed to bear whatever arms they please and are required to bear arms in accordance with the respective policies governing use of arms.
The United States Supreme Court even went so far as to disconnect the militia requirement (and if you read the history of the second amendment this makes sense that clause was originally there to protect people who had religious reasons for refusing to bear arms and ended up neutered to prevent abuses of that clause by the government to disarm its people)
the Supreme court had this to say in Heller V. DC
The Second Amendment protects an individual right to possess a
firearm unconnected with service in a militia, and to use that arm for
traditionally lawful purposes, such as self-defense within the home.
and on the militia clause
The Amendment’s prefatory clause announces a purpose, but
does not limit or expand the scope of the second part, the operative
clause. The operative clause’s text and history demonstrate that it
connotes an individual right to keep and bear arms