There is no "well regulated" standard and you aren't even using the definition that the founders meant. Again, the first part of the Second Amendment gives a reason why the people should have weapons without government intrusions and the folks who wrote the Constitution gave many other reasons in their writings with the biggest reason being that the people should have the means to revolt if the federal government went the way of Europe:
"If the representatives of the people betray their constituents, there is then no resource left but in the exertion of that original right of self-defense which is paramount to all positive forms of government, and which against the usurpations of the national rulers, may be exerted with infinitely better prospect of success than against those of the rulers of an individual state. In a single state, if the persons intrusted with supreme power become usurpers, the different parcels, subdivisions, or districts of which it consists, having no distinct government in each, can take no regular measures for defense. The citizens must rush tumultuously to arms, without concert, without system, without resource; except in their courage and despair."
- Alexander Hamilton, Federalist No. 28
Unalienable rights are those which God gave to man at the Creation, once and for all. By definition, since God granted such rights, governments could not take them away. In America, this fundamental truth is recognized and enshrined in our nation's birth certificate, the Declaration of Independence:
"[A]ll men are created equal...[and] are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."
It is important to understand that the very premise of our nation is the fact that these rights, based on Natural Law, are "God-given." If they are not given to us by an Authority higher than human government, then any government action to abolish those rights would be against God's will. Rights that are subject to government restriction or license are called a privilege rather than a right. The Founding Fathers understood this principle and created a revolution in political theory by enacting, for the first time in history, a government specifically established to protect the rights that had been given to man by God.
"That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed."