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.”
The circuit court’s opinion is only the latest volley in a long-simmering comma war. In a 2001 Fifth Circuit case, a group of anti-gun academics submitted an amicus curiae (friend of the court) brief arguing that the “unusual” commas of the Second Amendment support the collective rights interpretation. According to these amici, the founders’ use of commas reveals that what they really meant to say was “a well-regulated militia ... shall not be infringed.”
This is like porn for lawyers and grammarians.