"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." Second Amendment of the USA Constitution

I have never understood the Supreme Court's ruling that grants individuals the right to 'bear arms' and that the right shall not be infringed upon, meaning it shall not be curtailed or truncated or probably, regulated.

I understand its reasoning IF the qualifying phrase is disregarded. By why would anyone disregard it?

If I say: "My sister, being happily married, is the sibling I designate to raise my child in the event of...." What if my sister is no longer married, happily or not?

??