“Judicial power, as contradistinguished from the power of the laws, has no existence. Courts are the mere instrument of the laws, and can will nothing. When they are said to exercise a discretion, it is a mere legal discretion, a discretion to be exercised in discerning the course prescribed by the law; and when that is discerned, it is the duty of the Court to follow it. Judicial power is never exercised for the purpose of giving effect to the will of the Judge; always for the purpose of giving effect to the will of the Legislature [or, this author would add in another context, the makers of a constitution]; or in other words, to the will of the law.”
–Chief Justice John Marshall, Osborn v. Bank of the United States, 22 U.S. 738, 866 (1824).