Meddling in local enforcement, despite push-back from state and local authorities? What could possible go wrong...
(I don't know, I'm genuinely asking.)
The mayor is well aware of the practice being employed, and this is a way of saying it is distinctly unwelcome without minimizing the issues being used as a pretext for it.
The police union did, but in any case, for very good reasons of federalism, the normal and proper route for such a request for federal intervention in local civil order other than as a result of open rebellion by the State government against the Union is from the Governor of the State (who will consider the need for such a request in light of and assure coordination with any state response available and in use, such as state-level law enforcement, National Guard, etc.), not from the local police command.