In severing the link between residential address and school assignment, school choice policies have the potential to decrease school segregation and increase educational equity. Yet this promise is undermined when school choice creates greater opportunity for those who are already privileged while limiting access to students from historically marginalized groups. This study combines data from a new survey of local open enrollment policies in Metro Detroit, student-level administrative records, and geographic data to critically analyze the local discretion provided in Michigan's interdistrict school choice policy in relation to the goals of access to schools of choice, desegregation, and educational equity. I found that local school districts implement provisions of state policy in ways that restrict access to Black and economically disadvantaged students while creating pathways of opportunity for others. Districts are incentivized to implement these restrictions because of the inequities built into the state school funding formula and the racialized geography of Metro Detroit that is mechanized in district and county boundaries to restrict access. This study has implications for the regulation of local school choice markets and the role they play in increasing equitable public school opportunities.