In the case of D. C. v Heller shortly to be decided by the US Supreme Court, the central issue is the meaning of the Second Amendment to the US Constitution:
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.
One of the issues is whether the Second Amendment guarantees a private right, that is, a right of individuals to own and carry arms, or a public right, that is, a right of militias to own and carry arms, or both. Many advocates of restrictions on the right of individuals to own and carry arms promote the interpretation that the Second Amendment is meant only to protect the organized militia units, which, they typically argue, are now subsumed under the National Guard. For advocates of this interpretation, there is no individual right to own and carry weapons.
One aspect of this argument is the interpretation of the leading clause of the amendment. Advocates of the "public only" interpretation consider this clause to indicate that the needs of the militia are the exclusive motivation for the Second Amendment and that its scope is therefore limited to the militia. This issue has been discussed here on Language Log in the posts Once is cool, twice is queer and The right to keep and bear adjuncts.
Among the numerous amicus briefs submitted is the so-called "Linguists' Brief", written by Dennis E. Baron, Richard W. Bailey, and Jeffrey P. Kaplan. This brief argues that the Second Amendment protects only a public right on two grounds: the afore-mentioned interpretation of the leading clause, and the argument that the expression "bear arms" refers only to the organized military use of arms, not to individual use. They claim that the term "bear arms" is "an idiomatic expression that means 'to serve as a soldier, do military service'".
If true, this would be quite surprising, since there is what seems to me to be a very strong case, nicely put in the The Cato Institute Brief, that the right to bear arms in English law prior to the Bill of Rights was an individual right and that the Founders saw the Second Amendment and similar provisions in state constitutions as continuations and extensions of that tradition. A view contrary to that of the Linguists' Brief is presented by Clayton Cramer, a software engineer and historian, and Joseph Olson, a historian, in their paper What did 'Bear Arms' Mean in the Second Amendment. English usage of the late 18th century is not my area of expertise, but it seems to me that it is the non-linguists who have the stronger case.
The Linguists argument, like that of several previous authors on this topic, is that the phrase "bear arms" when used without modification in documents of the relevant period almost always is shown by context to refer to the military use of arms. Cramer and Olson, on the other hand, argue that to the extent this is true, it is due to selection bias:
If you look in databases consisting almost entirely of government documents, it should not be a surprise that most of the uses will be governmental in nature.
Searching more comprehensive collections of English language works published before 1820 shows that there are a number of uses that are clearly individual, and have nothing to do with military service.
Many of Cramer and Olson's examples are taken from British works, but this appears to me to be legitimate. In 1791 formal written American English usage was not, to my knowledge, significantly different from that of Great Britain. One such example is from Debrett's 1797 Collection of State Papers Relative to the War Against France, in a discussion of orders from the French Army on the occupation of "the country beyond the Rhine":
The inhabitants of the villages, who shall take arms against the French, shall be shot, and their houses burnt, as shall likewise all who bear arms without permission from the French generals.
While the phrase "take arms against the French" refers to military action, possibly collective rather than individual, "bear arms" here clearly refers to individual carrying of weapons. As Cramer and Olson note, it could refer to militia activity only in the extremely unlikely event that French generals were in the habit of giving permission to enemy militia to fight against them.
The case against the Linguists' Brief, though, does not rely entirely on British examples. Cramer and Olson cite the following passage about the history of Bologna from John Adams' 1787 A Defence of the Constitutions of the Government of the United States of America:
In order to purge the city of its many popular disorders, they were obliged to forbid a great number of persons, under grievous penalties, to enter the palace: nor was it permitted them to go about the city, nor to bear arms.
This is certainly a reference to individual bearing of arms, not to a militia.
Another example is the constructionof the term to "bear arms" by James Wilson. In the following passage from his Lectures on Law, he equates the passage in the Constitution of the State of Pennsylvania protecting the right "to bear arms in the defence of themselves" with the right of personal defense of one's self or house:
Homicide is enjoined when it is necessary for the defence of one's person or house.
With regard to the first, it is the great natural law of self-preservation, which, as we have seen, cannot be repealed, or superseded, or suspended by any human institution. This law, however, is expressly recognised in the constitution of Pennsylvania. "The right of the citizens to bear arms in the defence of themselves shall not be questioned." This is one of our many renewals of the Saxon regulations. "They were bound," says Mr. Selden, "to keep arms for the preservation of the kingdom, and of their own persons."
Wilson was a signer of the Declaration of Independence, a member of the Committee of Detail, which drafted the Constitution, and one of the six original justices of the Supreme Court, nominated by George Washington. He clearly took the right to "bear arms" to be an individual right.
An example discussed by both sides comes from a proposed amendment to the draft of the Constitution proposed by dissenting Pennsylvania delegates to the convention to ratify the US Constitution:
the people have the right to bear arms for the defense of themselves and their own state, or the United States, or for the purpose of killing game
There can be no question that bear arms here is not limited to military activity on the part of a militia.
Indeed, it is not clear to me that some examples cited by the linguists as evidence that bear arms refers to militia activity are correctly analyzed. Consider their discussion of James Madison's original draft of the Second Amendment:
The right of the people to keep and bear arms shall not be infringed; a well armed and well regulated militia being the best security of a free country: but no person religiously scrupulous of bearing arms, shall be compelled to render military service in person.
They claim that in the italicized religious scruples clause the phrase "bearing arms" can have no other meaning than "to serve as a soldier, do military service, fight", and that therefore the same term in the portion that was retained in the final version of the Bill of Rights must have the same meaning. The first claim is true: the phrase "bearing arms" in the religious scruples clause refers to military service. The second claim, that this requires the same term to have the same narrow meaning in the main portion of the amendment, is false. The narrowness of the meaning of "bearing arms" in the religious scruples clause flows not from the intrinsic meaning of the term but from the fact that we know that some people have religious scruples against warfare, while few if any people in late 18th century America, had religious objections to all uses of weapons. Had there been a vegetarian, pacificist sect in late colonial America that objected on religious grounds to all uses of weapons, even for personal defense, hunting, and target shooting, we would have no difficulty in reading the religious scruples clause as referring to all uses of weapons.
The linguists' approach to examples that they acknowledge contradict their claim that bear arms always refers to collective military activity is far from persuasive: they simply assert that such examples are "unidiomatic", "awkward", or "idiosyncratic". For example, here is their comment on the Pennsylvania dissenters' example above:
And adding, as did the Pennsylvania dissenters, the "for the purpose of killing game" language bends the idiom so far that it no longer is recognizable. It is decidedly unidiomatic. As Garry Wills aptly has put it, one does not bear arms against a rabbit… The statement by the court below that "it would hardly have been unusual for a writer at the time (or now) to have said that, after an attack on a house by thieves, the men set out to find them 'bearing arms'" appears equally unidiomatic… Not only would it have been unusual, it would have been awkward and idiosyncratic.
The logic here is circular: because they believe the expression "to bear arms" to have only a collective, military meaning, they dismiss contrary examples. There is no analysis of variation in usage supporting their contention that such examples are erroneous or idiosyncratic. The statement that they quote from Gary Wills, that "one does not bear arms against a rabbit", is irrelevant. The reason one does not "bear arms against a rabbit" is that "against" implies hostile action, but one does not normally consider rabbits to be the enemy, even if one is hunting them for their food and skin. If, in a postapocalyptic world, we were threatened by three meter tall intelligent carnivorous rabbits, we certainly might bear arms against them. A person who hunts rabbits as they are today cannot be said to bear arms against rabbits, but he or she may indeed be said to bear arms during the hunt.
In sum, while the Linguists' Brief may well reflect the view of the meaning of "bear arms" in 1791 formed on the basis of its authors experience reading material from that period, there appear to be clear and convincing examples of the use of this term in an individual, non-military, sense. The characterization of such examples in the Brief as anomalous is not supported by any sort of scientific linguistic analysis.
Note on Comments: Please confine comments to the question of the meaning of the Second Amendment and in particular to the meaning of "bear arms". Many people have strong feelings about guns. This is not the place to discuss them. In particular, please note that the meaning of the Second Amendment is a distinct question from what is good policy. It is quite possible to read the Second Amendment as protecting an individual right to possess and carry weapons while believing this to be poor policy, or to read it as protecting only the right of the people to organize militia, while believing that individuals ought to be able to possess and carry weapons.