Dave Kopel argues that the use of the word "the" in "THE right to keep and bear arms" indicates that the right was pre-existing.

A similar — though significantly different — argument has been made about "THE freedom of speech" in the first amendment, that including the word "THE" indicates that the right was pre-existing.

In the first amendment context, that argument misunderstands English grammar. When an of-phrase is newly coined, it should take an article, thus

"I recognize THE freedom of taking a shower whenever I please,"

NOT

"I recognize freedom of taking a shower whenever I please."

When an of-phrase becomes so common that it is treated as a single concept, only then is it idiomatic to drop the article. Thus, today we would usually say that a case "involves freedom of religion" or "involves freedom of speech." When a few hundred years ago, these phrases were not so common that they could be thought of as single concepts, we would have said that a case "involves THE freedom of religion" or "involves THE freedom of speech."

Now Dave Kopel's 2d amendment argument is different than the standard 1st amendment argument because an of-phrase is not involved:

"THE right TO keep and bear arms."

Although he is not entirely clear, I assume Kopel means that, if the right was not pre-existing, the 2d amendment might have said:

"A right to keep and bear arms."

But IMO idiom is not as reliable a guide here as Dave considers it to be. One can certainly use "A" to introduce rights thought to be pre-existing. Kopel does so himself in the post I am responding to. Kopel writes:

If the majority is right on this point, then the Stevens dissent is plainly wrong; the Second Amendment was intended to protect A personal right to arms for self-defense.

But is it also idiomatic to use "THE" when the right is not recognized as pre-existing? Yes. Idiomatically, I might write either:

I believe that each American should have THE right to drive as fast as he wants.

OR

I believe that each American should have A right to drive as fast as he wants.

Even though my examples presume that the right does not pre-exist, I still think that I might idiomatically refer to "THE right to drive as fast as he wants" or "A right to drive as fast as he wants." If I use "THE" to refer to a non-existent right, the word indicates which right I am refering to, in this example the particular right to drive as fast as he wants. IMO, using "THE" to refer to a right may just tell us which right is referenced, not that the right is pre-existing.

BTW, the best discussion of the use of articles before "of" phrases is in Wilson Follett's Modern American Usage (the versions edited by J. Barzun).