In mid-2011, the Florida state legislature passed House Bill 1355 (HB 1355) and in so doing placed new regulations on community organizations that historically have helped eligible Floridians register to vote. Among the legal changes promulgated by this bill were new regulations on the operations of groups like the League of Women Voters and a new oath, warning of prison time and fines, that voter registration agents were required to sign. Such changes raised the implicit costs that eligible Florida citizens faced when registering to vote, and we show that voter registrations across the state in the second half of 2011 dropped precipitously compared with registrations in the second half of 2007. This pattern is evident among registrants in general, among registrants age 20 and younger, and among individuals who registered as Democrats. Outside of HB 1355, we know of no credible explanations for these results. Our findings thus show how restrictions on the way that third-party organizations register voters can have tangible effects on actual registrations. Given that registration prior to an election is a civic necessity in Florida and in many other states, such restrictions have the potential to affect electoral outcomes as well.