There are no "international requirements" for an election. The United States, like every other nation, determines the matter for itself, disappointing as this may be to the goo-goo former president.
In fact, the U.S. Constitution leaves the matter up to the individual states:
Article II
Section 1. The executive power shall be vested in a President of the United States of America. He shall hold his office during the term of four years, and, together with the Vice President, chosen for the same term, be elected, as follows:
Each state shall appoint, in such manner as the Legislature thereof may direct, a number of electors, equal to the whole number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or person holding an office of trust or profit under the United States, shall be appointed an elector.