Cite as: 572 U. S. ____ (2014) 35 Opinion of ROBERTS, C. J. pothesize involve at least implicit agreements to circumvent the base limits—agreements that are already prohibited by the earmarking rules. See 11 CFR §110.6. The FEC might strengthen those rules further by, for example, defining how many candidates a PAC must support in order to ensure that “a substantial portion” of a donor’s contribution is not rerouted to a certain candidate. §110.1(h)(2). Congress might also consider a modified version of the aggregate limits, such as one that prohibits donors who have contributed the current maximum sums from further contributing to political committees that have indicated they will support candidates to whom the donor has already contributed. To be sure, the existing earmarking provision does not define “the outer limit of acceptable tailoring.” Colorado Republican Federal Campaign Comm., 533 U. S., at 462. But tighter rules could have a significant effect, especially when adopted in concert with other measures. We do not mean to opine on the validity of any particular proposal. The point is that there are numerous alternative approaches available to Congress to prevent circumvention of the base limits. D Finally, disclosure of contributions minimizes the potential for abuse of the campaign finance system. Disclosure requirements are in part “justified based on a governmental interest in ‘provid[ing] the electorate with information’ about the sources of election-related spending.” Citizens United, 558 U. S., at 367 (quoting Buckley, supra, at 66). They may also “deter actual corruption and avoid the appearance of corruption by exposing large contributions and expenditures to the light of publicity.” Id., at 67. Disclosure requirements burden speech, but—unlike the aggregate limits—they do not impose a ceiling on speech. Citizens United, supra, at 366; but see McConnell, supra,