Cops should not be allowed any power that is not available to every person, by virtue of their automatic eligibility for the county posse under authority of the sheriff, and for the state militia under authority of the governor.
Cops are supposed to be professionals, with keeping the civil order of their state and/or county and/or municipality as their full-time job, but the authority to arrest criminals historically extends from the sheriff of the county, to every person whom he or she may designate, either orally or in writing. If the sheriff asked for assistance from an ordinary person, and they effected an arrest, that was legally an official act of the sheriff. Similar extension-of-authority constructs exist for a municipal mayor/council, state governor, and federal president.
Without a preexisting order to assist, as one might have as a municipal cop or full-time county deputy, there is no official cover for an arrest, and the person making one would have personal liability, if they made a mistake. That privilege of immunity for mistakes made during establishment or maintenance of civil order is supposed to keep professional cops from being too fearful of civil liability lawsuit to do their jobs effectively. I would argue that they are now not fearful enough to conduct themselves in a manner consistent with their positions in the community, as part of it, simply being persons who have been given a standing order to assist the office of the president/governor/sheriff/mayor in their duty to keep civil order. They have now set themselves apart from the communities in which they live, behind the cordon of their thin blue lines, as adversaries to those whom they see as enemies of civil order.
As such, they have become blind to those occasions on which their actions are actually upsetting to the civil order. In other words, they get into some crazy bullshit legal arguments, and sometimes get away with it.
The privilege they enjoy is actually in having their personal actions taken as extensions of a higher lawful authority, rather than as their own.
It is established that the state has the authority to require that motor vehicle owners permanently affix a license plate to their vehicles, which remains the property of the state, and not remove it, and to return it to a designated authority on demand. But this is all written into public law. You can't just arbitrarily extend that power to some cop shop's magnetic GPS tracker. If you want it to be a crime to remove it, you have to write that into its own law. Otherwise, you have to follow the same law for theft (or unlawful conversion) as everyone else. And that opens up a reciprocal liability for putting your property on someone else's property without their authorization.
I suppose the opsec moral of the story is to drop found trackers onto the public road, or report it as lost property, instead of leaving it inside a locker. Putting a classified ad for lost property in the public notices section of the local paper for three consecutive weeks might have been a fun experiment in "fruit of the poisoned tree" lawyering.