“ Whenever in the course of litigation such a defect in the proceedings is brought to the court's attention, it may set aside any adjudication thus procured and dismiss the cause without entering judgment on the merits. It is the court's duty to do so where, as here, the public interest has been placed at hazard by the amenities of parties to a suit conducted under the domination of only one of them. The district court should have granted the Government's motion to dismiss the suit as collusive. ”

“ But it does insist that the affidavits disclose the absence of a genuine adversary issue between the parties, without which a court may not safely proceed to judgment, especially when it assumes the grave responsibility of passing upon the constitutional validity of legislative action. Even in a litigation where only private rights are involved, the judgment will not be allowed to stand where one of the parties has dominated the conduct of the suit by payment of the fees of both. ”

“ It does not assume the 'honest and actual antagonistic assertion of rights' to be adjudicated-a safeguard essential to the integrity of the judicial process, and one which we have held to be indispensable to adjudication of constitutional questions by this Court. ”