This paper examines the impacts of the Loi relative à la Solidarité et au renouvellement urbains (SRU) law, which was designed to encourage more equitable distribution of affordable housing in French metropolitan areas to reduce the concentration of families living in poverty and increase access to opportunity. This regulation mandates that many urban municipalities designate 25 percent of their housing stock to units affordable to households with low and moderate incomes by 2025. Communities that do not comply face budgetary penalties. I find that the law was associated with a flattening out of the distribution of affordable housing, with the most exclusionary cities and suburbs experiencing a fivefold increase in availability. The effectiveness of the law increased when penalties expanded. I also show how a similar requirement could be applied to segregated regions in the United States.