660 ASHCROFT v. AMERICAN CIVIL LIBERTIES UNION Opinion of the Court (COPA), 112 Stat. 2681-736, codified at 47 U. S. C. § 231. We must decide whether the Court of Appeals was correct to affirm a ruling by the District Court that enforcement of COPA should be enjoined because the statute likely violates the First Amendment. In enacting COPA, Congress gave consideration to our earlier decisions on this subject, in particular the decision in Reno v. American Civil Liberties Union, 521 U. S. 844 (1997). For that reason, "the Judiciary must proceed with caution and.., with care before invalidating the Act." Ashcroft v. American Civil Liberties Union, 535 U. S. 564, 592 (2002) (Ashcroft I) (KENNEDY, J., concurring in judgment). The imperative of according respect to the Congress, however, does not permit us to depart from well-established First Amendment principles. Instead, we must hold the Government to its constitutional burden of proof. Content-based prohibitions, enforced by severe criminal penalties, have the constant potential to be a repressive force in the lives and thoughts of a free people. To guard against that threat the Constitution demands that content-based restrictions on speech be presumed invalid, R. A. V v. St. Paul, 505 U. S. 377, 382 (1992), and that the Government bear the burden of showing their constitutionality, United States v. Playboy Entertainment Group, Inc., 529 U. S. 803, 817 (2000). This is true even when Congress twice has attempted to find a constitutional means to restrict, and punish, the speech in question. This case comes to the Court on certiorari review of an appeal from the decision of the District Court granting a preliminary injunction. The Court of Appeals reviewed the decision of the District Court for abuse of discretion. Under that standard, the Court of Appeals was correct to conclude that the District Court did not abuse its discretion in granting the preliminary injunction. The Government has failed, at this point, to rebut the plaintiffs' contention that there are plausible, less restrictive alternatives to the statute. Sub-