The EO limiting the powers of independent agencies actually seems to extend unitary executive theory to the president's subordinates in its preamble.

www.federalregister.gov/documents/20...

Clinton interprets the act as unconstitutional and advisory in nature because it would direct the president in matters of foreign policy, despite his agreeing with the goal.

So there is some precedent for jealously guarding "foreign policy" that Trump could point to if he realizes it exists.

Secondly, presidents in the past *have* ignored the other branches when matters are technically in the realm of foreign policy. See President Clinton's signing statement on International Dolphin Conservation Program Act of 1997.

www.presidency.ucsb.edu/documents/st...