James Buchanan actually said...

"Without the authority of Congress the Executive can not lawfully direct any force, however near it may be to the scene of difficulty, to enter the territory of Mexico, Nicaragua, or New Granada for th..."

"On the other hand, should the Executive interpose, and especially should the result prove disastrous and valuable lives be lost, he might subject himself to severe censure for having assumed a power n..."

"It can not legitimately resort to force without the direct authority of Congress, except in resisting and repelling hostile attacks."

"He can resort to no hostile act."