The US signed the
Sino-American Mutual Defense Treaty with Taiwan. Congress ratified the
treaty and it came into force.
Later, President Carter wanted
to establish diplomatic relations with China, so he unilaterally cancelled
the treaty with Taiwan to get the Chinese to agree to relations.
He did not consult with
Congress, or ask them to ratify the nullification.
Senator Goldwater sued for an
injunction, claiming that in order to nullify a treaty, the President
needs to get the advice and consent of the Senate.
See Article II, Section 2, which states that the President cannot make
treaties without a Senate majority 2/3rds vote.
The Constitution says
nothing about how to break a
treaty.
The US Supreme Court dismissed
the case.
The US Supreme Court found
that this was a political question,
and so it could not be decided by the courts.
In a concurrence, it was
argued that the issue itself, the powers of the President to break
treaties without Congressional approval, would have been arguable had
Congress issued a formal opposition through a resolution to the termination
of the treaty.
This would have turned the
case into a constitutional debate between the executive powers granted to
the President against the legislative powers granted to Congress. As the
case stood, however, it was simply a dispute between the executive and
legislative branches of government, and was political in nature.
In a dissent, it was argued
that "the issue of decisionmaking authority must be resolved as a
matter of constitutional law, not political discretion; accordingly, it
falls within the competence of the courts."
The case is a good example of
the Political Question Doctrine.
As it stands now, there is no
official ruling on whether the President has the power to break a treaty without the approval of Congress.