Cite as: 542 U. S. 656 (2004) Syllabus an established review standard, Walters v. National Assn. of Radiation Survivors, 473 U. S. 305, 336, the injunction must be upheld and the case remanded for trial on the merits if the underlying constitutional question is close. There is therefore no need to consider the broader constructions of the statute adopted by the Court of Appeals. The District Court concentrated primarily on the argument that there are plausible, less restrictive alternatives to COPA. See Reno, 521 U. S., at 874. When plaintiffs challenge a content-based speech restriction, the Government has the burden to prove that the proposed alternatives will not be as effective as the challenged statute. Ibid. The purpose of the test is to ensure that speech is restricted no further than is necessary to accomplish Congress' goal. The District Court's conclusion that respondents were likely to prevail was not an abuse of discretion, because, on the record, the Government has not met its burden. Most importantly, respondents propose that blocking and filtering software is a less restrictive alternative, and the Government had not shown it would be likely to disprove that contention at trial. Filters impose selective restrictions on speech at the receiving end, not universal restrictions at the source. Under a filtering regime, childless adults may gain access to speech they have a right to see without having to identify themselves or provide their credit card information. Even adults with children may obtain access to the same speech on the same terms simply by turning off the filter on their home computers. Promoting filter use does not condemn as criminal any category of speech, and so the potential chilling effect is eliminated, or at least much diminished. Filters, moreover, may well be more effective than COPA. First, the record demonstrates that a filter can prevent minors from seeing all pornography, not just pornography posted to the Web from America. That COPA does not prevent minors from accessing foreign harmful materials alone makes it possible that filtering software might be more effective in serving Congress' goals. COPA's effectiveness is likely to diminish even further if it is upheld, because providers of the materials covered by the statute simply can move their operations overseas. In addition, the District Court found that verification systems may be subject to evasion and circumvention, e. g., by minors who have their own credit cards. Finally, filters also may be more effective because they can be applied to all forms of Internet communication, including e-mail, not just the World Wide Web. Filtering's superiority to COPA is confirmed by the explicit findings of the Commission on Child Online Protection, which Congress created to evaluate the relative merits of different means of restricting minors' ability to gain access to harmful materials on the Internet. 47 U. S. C. §231, note. Although filtering software is not a perfect solution because it may block some materials