SNIP I'll be "that guy" and say, "Why shouldn't we be able to carry into a court room?"
It probably dates from the days when the king enforced unpopular laws.
It makes no sense, really, in light of the rational and history behind trials.
Go back to the days of Henry II in the late 1100's. Prior to that, trials were by ordeal--carrying a hot coal so many paces and then checking whether the wound was healing properly after so many days, or being tossed into water to float or sink (water would reject--float--the criminal). Trial by ordeal was supplanted by trial by judge and jury. Henry II instructed royal judges to ride circuit and take jurisdiction of cases formerly tried by the lords of the manors wherein the offense was committed. Back then, you had a choice: trial by ordeal, or trial by judge and jury. You had to
consent to be tried by a judge and jury. This is the basis for certain features in the legal system, for example, pleading guilty or not guilty. This is why during Elizabethan times, if you refused to plead, the judge did not automatically enter a plea of not-guilty. You were tortured by pressing with iron--you were laid on the cell floor, covered with a plank, upon which was placed "as much iron as he could bear, and then more". You were not tortured to confess, you were tortured to plead. The government couldn't try you without your plea. The government couldn't try you without your consent.*
The other, and more important, aspect of this was that trials were "by the country". This is the reference in Magna Carta to "trial by the country". And, later references to "trial by the vicinage", and "trial by a jury of his peers." There was even a time when the accused, in being asked his plea was also asked whether he consented to be tried by the country--a trial by his peers. These were important legal formalities.
Henry II's circuit judges didn't preside over a jury trial. One of Henry's innovations was the sheriff selecting a jury to state the facts of the case to the judge. It was presumed that the people of the town or vicinity knew the facts of the case from their social interactions and were expected (required under oath) to inform the judge of what they knew. This was the beginnings of the jury system.
The quick view is that you sought relief from trial by ordeal in the arms of the royal judge with a jury of your peers informing the judge of the facts of your case. Which slowly over time evolved into the jury trial system we have today.
So, ultimately, today, a trial by jury is a trial presided over by the government judge, but decided by the people.
So, if the trial is by the people, then why disarm the people in their court room? Just let everybody be armed and you'll have more security than you need.
Unless, of course, you're the government and have subverted the process, and are enforcing unpopular or unconstitutional laws.
Note: The history stuff is from memory from two books by Leonard Levy,
The Origins of the Bill of Rights and
The Origins of the Fifth Amendment: The Right Against Self-incrimination. Since its from memory, something might be a little off; don't take it too firmly.
Note: Those two books are still in print. I highly recommend them. The book on the 5A won a Pulitzer Prize in history.
*I got five dollars that says government has usurped its role in trials. What was the social and political atmosphere toward government at a time when government needed your consent to try you? It couldn't just try you like today. What changed? How did people and the common law view the king if the king couldn't just up and seize people and try them without the consent of the accused? Whereas today, the judge will enter a plea of not guilty and not even bother with your consent. Hmmmm. Makes me wonder.
