That precedent goes all the way back to President Jefferson and his Secretary of State James Madison.
The key word is "defense".
MEMO TO DEMOCRATS, MSNBC, AND OTHER LIBERALS: If you disagree with the above, please state even one limit on the President's power to act militarily in defense of America. (The question is, what ways would YOU want to tie the President's hands in defending us from an attack, hmmmm?)