Actually the original statement about the Posse Comitatis Act still only applying to the Army (and by extention, to the Air Force) is still technically correct. The ammendment cedes to SecDef (the Executive branch)the "regulation", thereby expressly circumventing the "legislation" or "law" of Congress. In fact, the Marines were once called out to preserve the law of the land (trivia question: where and under what circumstances - no fair if a Marine answers).

Under separate circumstances the National Guard already has a form of this very authority, thus being used to put down riots, looting etc. under martial law.

And folks, the "Cabal of Officers" plot has figured in many B-grade thrillers with nary a twitch of reality. For God's sake people, this is America, not some third rate European, Asian, South American, or African country. (Second trivia question: America is one of the very few countries in the World which has not had a military coup succeed in over turning the duly constituted government of that nation; name some others...

If some General wants power, he runs for President, like Ike, Grant or Washington (or not, like Powell). And consider that after WWII, Russian citizens had multiples of guns for every citizen (and still do), yet Stalin did what he wanted, when he wanted. It has never been about taking guns away; it's about taking away the will to fight. If you keep the will, the guns come easy.

BTW, the First Ammendment, by virtue of the UCMJ, does not apply to members of the Armed Forces. In fact, by well established precedent, the truth of the statement is not a bar to prosecution, (as every young officer is taught). As we Marines used to say, "We use deceit, death, and destruction to preserve truth, honesty, justice, and the American Way of Life". (A world the protected will never know...)