An expert that Alphabet’s Sidewalk Labs hired to oversee privacy issues related to an ambitious smart-city project has quit over proposed data-collection practices.

Details: Sidewalk Labs is trying to build a futuristic neighborhood called Quayside on Toronto’s waterfront. The development is the first big assignment for the Google sister company, which was founded in 2015 to develop technology to alleviate urban problems.

But: The project keeps running into obstacles. In August, it delayed the release of its final development plan because of local resistance. Now privacy concerns have compelled Ann Cavoukian, the former privacy commissioner for the province of Ontario, to leave the project. She says she resigned because third-party companies and developers might be able to access identifiable information about Quayside residents once the project gets built. (Sidewalk Labs says it should not formulate rules for third parties on its own and proposes creating a “Civic Data Trust” to devise that policy instead.) Another advisor also left in recent weeks over privacy issues.

Why it matters: Sidewalk Labs intends to sell technologies originally developed for Quayside to other cities. That means these privacy practices could affect a number of people, potentially around the world. The controversy also feeds the ongoing debate of whether big tech companies are doing enough to protect user data.