Mayor Bill de Blasio's office defended the measures, which were intended to reduce traffic and clear streets for buses, bikes and pedestrians. A spokesperson contended that the moves were both legal and provide "needed relief" to both NYC streets and existing drivers.

Uber and rivals like Lyft have acknowledged that their services can make traffic worse. However, they've typically wanted to alleviate the burden on their own terms, and that has typically meant avoiding caps. They're unlikely to simply accept the rules, and it's not clear that a compromise is on the horizon.