No one shall be subjected to arbitrary interference with his privacy, family, home or correspondence, nor to attacks upon his honour and reputation. Everyone has the right to the protection of the law against such interference or attacks.
via The Universal Declaration of Human Rights Article XII
Passed by the UN General Assembly in 1948 and became international law in 1976. Note that privacy of correspondence is specifically protected. Spying on Americans is un-Constitutional while spying by the American government on non-Americans is a clear and direct violation of international law.
As the United States slides toward despotism can it please avoid dragging the rest of the world behind?