I was under the impression that political constitutions (at least in the Western republican tradition) were in the business of enumerating government powers rather than merely paring back an omnipotent ruler. Your statement suggests that governments have all powers not expressly denied them in the constitution. Such a belief puts you at odds with the Ninth Amendment of the U.S. Constitution. Something that a Justice of the Supreme Court should know.
In any case, the CoD was violating the Chilean constitution. Much like the American system, article 39-1a of Chile's 1925 constitution gives the lower house the power to accuse the president of "actos de su administracion en que haya comprometido gravemente el honor o la seguridad del Estado, o infrinjido abiertamente la Constitucion o las leyes" and article 42-1a gives the Senate the power to convict the president of these charges with a 2/3 supermajority.
So, given that, I would say that the CoD's call for a military coup, and Pinochet's answer to that call, violated article 4, which I quote in full: "Ninguna majistratura, ninguna persona, ni reunion de personas pueden atribuirse, ni aún a pretesto de circunstancias estraordinarias, otra autoridad o derechos que los que expresamente se les hayan conferido por les leyes. Todo acto en contravenvion a este artículo es nulo."
Sounds pretty straightforward to me. In American terms, Allende was "impeached" but not "convicted" when the lower house called for a military intervention and Pinochet responded by overthrowing the elected government.
To my knowledge there was nothing in the constitution actively barring the Chamber of Deputies from asking the police and military to defend the constitution against its attackers.
Certainly they could ask as a group of individuals, but it was not a power granted to the CoD and thus not an act given sanction or legitimacy by the Chilean constitution.
There wasn't a process spelling out step by step how they were to do this, but certainly nothing prohibiting them from doing it, particularly when facing a threat of constitutional overthrow itself.
In fact, article 4 makes it clear that claims of "extraordinary circumstances" do not constitute a legitimate excuse for overstepping constitutionally defined powers. Again:
"Ninguna majistratura, ninguna persona, ni reunion de personas pueden atribuirse, ni aún a pretesto de circunstancias estraordinarias, otra autoridad o derechos que los que expresamente se les hayan conferido por les leyes. Todo acto en contravenvion a este artículo es nulo."
So by calling for a coup, the CoD was overstepping its authority (usurping the Senate's power to convict or acquit an accused president) and thus acting unconstitutionally.
Your statement suggests that governments have all powers not expressly denied them in the constitution. Such a belief puts you at odds with the Ninth Amendment of the U.S. Constitution.
I'm amazed at how overlooked the Ninth Amendment actually is. Its importance belies the relatively high number it holds in the Bill of Rights.
In my opinion, it is one of the most important. Without it, the Federal Government could just invent new powers for itself at a whim. The Ninth is the last stand against tyranny, giving freedom the benefit of the doubt where the Constitution is silent.