I do not agree with the philosophy that the police should be allowed to do whatever they want as long as it wasn't explicitly prohibited in advance. That is the result of relying on ordinances that enumerate "what things require consent". A blanket expenditure limit is a better system in theory, but the article posted here demonstrates that it should actually be something like a "value added" limit. I am disagreeing with you that surveillance is the only concern in this thread. Private donations to the police of any kind are concerning when they bypass what is supposed to be a blanket limit on police power.

I honestly don't see the issue with private donations. Either it's something you want the police to have or it isn't. So the system needs to be structured to prevent them unilaterally deploying things that the bulk of the populace might not approve of.

I agree that a blacklist approach doesn't work. But neither does an expenditure limit. A value added limit is I think just a roundabout way of expressing a whitelist approach? Which seems like the only sensible solution to me. Ideally all deployments should require case-by-case approval unless an ordinance is passed to blanket approve an entire technology class for a specific type of usage.