The second amendment was written to secure the individual right to keep and bear arms as part of a well regulated state Militia from federal infringement. If Congress refused to arm the Militias (under Article I, Section 8), Congress could not stop individuals from arming themselves to form a well regulated state Militia.
"Arms" are defined by each state. How individuals are to keep and bear them is up to each state. If Congress infinges on any of these areas, the state has standing to challenge the law in federal court.
Simple. Clean. No guesswork. No restrictions. No justifications.
When the second amendment is interpreted correctly.
The individual right to keep and bear arms outside of a Militia is protected by state constitutions. The State Supreme Court will define "arms", "keep" and "bear" for the citizens of that particular state based on their interpretation of the state constitution.
Four words in the Constitution make all gun laws unconstitutional: “shall not be infringed.” The number of gun laws on the books at both the federal and state level is a measure of just how much tyranny we live under. It is also a measure of the cowardice of the US citizenry. The fact that we have this discussion over and over again shows just how far this nation has departed from what the Founders had in mind and how weak are “the people”.