“(a) Except as provided in subsection (b), notwithstanding any other provision of law, no United States district court shall issue any order providing for injunctive relief, except in the case of such an order that is applicable only to limit the actions of a party to the case before such district court with respect to the party seeking injunctive relief from such district court and non-parties represented by such a party acting in a representative capacity pursuant to the Federal Rules of Civil Procedure.

“(b) If a case is brought by two or more States located in different circuits challenging an action by the executive branch, that case shall be referred to a three-judge panel selected pursuant to section 2284, except that the selection of judges shall be random, and not by the chief judge of the circuit. The three-judge panel may issue an injunction that would otherwise be prohibited under subsection (a), and shall consider the interest of justice, the risk of irreparable harm to non-parties, and the preservation of the constitutional separation of powers in determining whether to issue such an order.

“(c) An appeal of an order granting or denying injunctive relief pursuant to subsection (b) may lie to the circuit embracing the district or to the Supreme Court, at the preference of the party.”.