In the case of Wiener v. United States (357 U.S. 349 (1958)), it was recognized that Congress has the power to create independent agencies; government entities that are free from the Presidential removal power established in Myers v. United States (272 U.S. 52 (1926)). Wiener was a commissioner of an independent agency (War Claims Commission), and had been fired by President Eisenhower. Other exampled of independent agencies include the Federal Trade Commission and the Federal Communications Commission. These agencies don't just enforce laws (which would make them exclusively Executive Branch agencies). They also have quasi-legislative and/or quasi-judicial functions. The President has the power to appoint people to these offices, but not the power to fire them without the consent of Congress. Since these agencies are not completely Executive Branch in nature, they don't fall exclusively under the President's purview like Myers did in Myers v. United States. The idea is that these agencies need to be able to operate free from Presidential threats, similar to how the President can't fire a judge. The concept of these independent agencies appears nowhere in the Constitution. See Buckley v. Valeo (424 U.S. 1 (1976)) which ruled that an exclusively Executive Branch agency (FEC) could not have officers who reported to the Legislative Branch.