We study the provision of an excludable public good to discuss whether the imposition of participation constraints is desirable. It is shown that this question may equivalently be cast as follows: should a firm that produces a public good receive tax revenues, or face a self-financing requirement. The main result is that the desirability of participation constraints is shaped by an equity-efficiency tradeoff: While first-best is out of reach with participation constraints, their imposition yields a more equitable distribution of the surplus. This result relies on an incomplete contracts perspective. With a benevolent mechanism designer, participation constraints are never desirable.