Cite as: 542 U. S. 656 (2004) Opinion of the Court percentage of time that blocking and filtering technology is over- or underinclusive." Ibid. In the absence of a showing as to the relative effectiveness of COPA and the alternatives proposed by respondents, it was not an abuse of discretion for the District Court to grant the preliminary injunction. The Government's burden is not merely to show that a proposed less restrictive alternative has some flaws; its burden is to show that it is less effective. Reno, 521 U. S., at 874. It is not enough for the Government to show that COPA has some effect. Nor do respondents bear a burden to introduce, or offer to introduce, evidence that their proposed alternatives are more effective. The Government has the burden to show they are less so. The Government having failed to carry its burden, it was not an abuse of discretion for the District Court to grant the preliminary injunction. One argument to the contrary is worth mentioning-the argument that filtering software is not an available alternative because Congress may not require it to be used. That argument carries little weight, because Congress undoubtedly may act to encourage the use of filters. We have held that Congress can give strong incentives to schools and libraries to use them. United States v. American Library Assn., Inc., 539 U. S. 194 (2003). It could also take steps to promote their development by industry, and their use by parents. It is incorrect, for that reason, to say that filters are part of the current regulatory status quo. The need for parental cooperation does not automatically disqualify a proposed less restrictive alternative. Playboy Entertainment Group, 529 U. S., at 824 ("A court should not assume a plausible, less restrictive alternative would be ineffective; and a court should not presume parents, given full information, will fail to act'). In enacting COPA, Congress said its goal was to prevent the "widespread availability of the Internet" from providing "opportunities for minors to access materials through the World Wide Web in a manner that can frustrate