Private school leaders weigh costs and benefits when deciding whether to participate in school voucher programs. Regulatory costs associated with accepting voucher funding could reduce private school leaders' willingness to participate. We test this hypothesis through the first random assignment analysis of the effects of various regulations on the expressed willingness of private school leaders to participate in hypothetical voucher programs that draws upon national data. We randomly assign different regulations to U.S. private school leaders and ask them whether they would participate in a hypothetical school voucher program during the following school year. Relative to no regulations, we find that open-enrollment mandates reduce the likelihood that private school leaders report being certain to participate in a hypothetical choice program by about 14 percentage points, or 67%. The requirement that private schools accept the voucher funding amount as payment-in-full reduces the likelihood that private school leaders report being certain to participate by 16 percentage points, or 77%. Some regulations are more likely to deter private schools with higher reported tuitions, higher enrollment trends, more specialization, and more climate problems.