Updated: Aug 15, 2019
A lot of people argue that we no long have or need militias and therefore the second amendment is no longer valid.
First, militias certainly do still exist, although they may no longer be state funded. An arguement could be made that the National Guard is a militia, but let's not go there today.
Second, if we still need militias in modern America depends partly on what you think of their purpose. Some believe that a militia is to help the military when needed to fight foreign forces. Others believe the purpose of a militia is to fight our own government if needed. Still others believe that their purpose is to fight to protect our rights regardless of who they have to fight. Again, this is not for today's discussion.
Today, let us look at the basic text of the second amendment and dissect the sentence as we did in primary school.
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
What portion or portions of this make a complete thought? What parts can stand alone as a complete sentence?
The first half, "A well regulated Militia, being necessary to the security of a free state..." though important, is not a complete thought. The founding fathers could have easily made it a complete thought by simply replacing the word "being" with the word "is". In which case it would have read 'A well regulated militia is necessary to the security of a free state." That simple change would have made any argument about the need and/or purpose of a militia supremely relevant. Our founding fathers had a good grasp of the English language, yet chose not to make the first half of the second amendment a declarative complete thought.
The first two commas separate out a dependent clause, ", being necessary to the security of a free state,". This portion only applies to the first portion, "A well regulated militia..."
The second half of the second amendment is a declarative statement . "the right of the people to keep and bear arms, shall not be infringed". This portion can stand alone. This is the stance that the US Supreme Court took when striking down a gun ban in Washington D.C.
"According to the court, the second comma divides the amendment into two clauses: one 'prefatory' and the other 'operative.' On this reading, the bit about a well-regulated militia is just preliminary throat clearing; the framers don't really get down to business until they start talking about 'the right of the people ... shall not be infringed,'"
Thomas Jefferson proposed a "corrected" version of the second amendment that only had one comma. His version only included the second comma. This supports the Supreme Court's findings. Unfortunately for clarity sake, Thomas Jefferson did not make his suggestion until after the proposed amendment had all ready been sent to the states for radification because he had been in Paris.
The only grammatical argument that can be made to support restricting gun rights would be if the section between all three commas is one large dependent clause. That would leave "A well regulated militia...shall not be infringed". This would take us back to the opening questions about the need and purpose for the militia.
Intentional or not, the only declarative portion of the second ammendment as it is written is that the right of the people to keep and bear arms shall not be infringed.