I plan live events these days and the off duty cop shakedown is so real. Good luck getting really any permit. “Oh you’re hiring private security? We don’t think your security plan is sufficient to keep everyone safe.”
I'm positive that corruption like GP described is able to coexist with scenarios like yours where everything's above board, but given you are hiring the off-duty police voluntarily, you haven't established that there wouldn't be repercussions for not doing so.
I suppose that’s how they continue to get away with it. We’re all hoping someone else falls on their sword.
This is a good tactic in many other situations as well.
extortion is unrelated of the exact words used but the intend
that clever phrasing can make you avoid extortion charges or similar is a common misbelive
if a cop gets away with a clear extortionist behavior it's because the prosecutor lets them and uses formulation as a shallow excuse not because clever formulations protect you from the law