...before that court as in other cases in which the United States Is interested. And the Attorney General may, whenever he deems it for the interest of the United States, conduct and argue any case In any court of the United States, or may require the solicitor general...

...General shall, conduct and argue suits and writs of error and appeals in the Supreme Court and suits in the Court of Claims in which the United States is interested, and the Attorney General may, whenever he deems it for the interest of the United States, either in person...

...the Attorney-General and Solicitor-General conduct and argue all cases in the Supreme Court and in the Court of Claims in which the United States is interested; and, when the Attorney-General so directs, any such case in any court of the United States may l>e conducted...