Mike wrote:
Yes the Constitution can be amended, but there are a couple points to consider.
Amendments 1-10 are the Bill of Rights, a codification of that which pre-exists civil law. They are not civil rights, i.e. rights granted by government.
The amendment process is quite involved, and though theoretically possible, it doesn't make any sense to say the Congress can repeal free speech, freedom of the press, freedom of religion, etc. It's not within their realm to repeal, seeing as how these are not rights given by government in the first place. Naturally it would be political suicide for them to attempt to do so. They oft need be reminded that it is their duty to preserve these rights.

HINT: keyword = AMENDMENT

Mike wrote:
The government is subject to the supreme law of the land, and must abide it. It cannot legally make laws overriding it. Since the citizenry is also subject to that supreme law, and their legal rights codified in it, no law contradicting it can be abided.
As you said the instituted law must be obeyed, but with the qualification that no law may be instituted which contradicts the highest law.