Actually, this question goes further in depth than just relating to Article III, Section iii of the United States constitution which defines treason.
“Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.”
The militia’s purpose is to suppress insurrections, not foment them according to Article 1, Section 8, Clause 15:
“To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;”
Insurrection being defined by Webster (a good American Dictionary, not that evil
OED) as:
an act or instance of revolting against civil authority or an established government
Dennis v. United States, 341 U.S. 494 (1951) mentions the insurrectionist theory as being off the table:
The obvious purpose of the statute is to protect existing Government, not from change by peaceable, lawful and constitutional means, but from change by violence, revolution and terrorism. That it is within the power of the Congress to protect the Government of the United States from armed rebellion is a proposition which requires little discussion. Whatever theoretical merit there may be to the argument that there is a “right” to rebellion against dictatorial governments is without force where the existing structure of the government provides for peaceful and orderly change. We reject any principle of governmental helplessness in the face of preparation for revolution, which principle, carried to its logical conclusion, must lead to anarchy. No one could conceive that it is not within the power of Congress to prohibit acts intended to overthrow the Government by force and violence. The question with which we are concerned here is not whether Congress has such power, but whether the means which it has employed conflict with the First and Fifth Amendments to the Constitution.
Explain how a document that says that the Militia is to suppress insurrections and only lists one crime, treason, which is pretty much the same thing as insurrection, allows for people to commit treason using the Second Amendment:
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.
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