The biggest problem is our chickenshit prosecutors, not a lack of criminal laws that apply to the police. We could have more, certainly, but we don't even apply the ones we have.
However, referencing a completely different law kind of makes my point. Straight "kidnapping" and "false imprisonment" would be the appropriate charges. Yet the corrupt cop is still allowed to hide behind their nominal position, despite deliberately acting outside its authority.
When I wrote my comment I was thinking of the TSA, which has done many things that were later slapped down by the court, but with no punishment for having violated the law for so long. Because despite being illegal, their actions were "policy" and thus apparently every crime they already committed is let slide.
If the problem were just corrupt prosecutors, then we would expect to still see plenty of civil suits - individuals can still sue on their own. Yet if you ask an attorney about doing so, they'll just laugh. And even when the situation is serious enough to warrant a civil suit, it's still the city getting sued rather than the person who happens to be employed as an officer. The equivalent in the tech world would be cracking as a hobby, and when caught passing the responsibility off to your employer because you were using your work-provided laptop. But obviously that doesn't fly in the private sector.
So the best that can happen after years of court time (with the government agents being paid the whole time), is a court judgement to stop doing something. There is no personal liability for the offending agents, no liquidated damages for the victims, no conspiracy charges for management's illegal policies, etc.
In general, the state has a massive blindspot towards damages that it itself inflicts. As we can expect from any natural system, it has settled into creating ever more externalities. Cops have been abusing "you might beat the rap, but you can't beat the ride" for forever. Now that moral hazard is everywhere.
In a just society, much of the state's activities would be viewed as just another actor on a level playing field, and would therefore be directly liable the damages it itself causes to innocent parties.