Happened upon this thread, and reminded me of an interesting situation recently.

My girlfriend took my car to the courthouse a few weeks ago to pay a driving ticket. My car keys (both sets) had a handcuff key on the keyring. This was merely left on from my stint working as an armed private security guard 10 years ago.

Now, I wasn't present, so the rest of this just goes by what she says, but after placing the keys in the basket next to the WTMD, the county cop noticed the key, ordered her to remove it from the keyring for confiscation, and was threatened with arrest if she didn't comply. She surrendered it, but asked for it back upon exiting and was denied.

AFAIK, there is no law in IL regarding handcuff keys, and even still to this day I keep my license up to date for private security (not that I ever want to use it again), in which profession handcuffs are standard issue. While I understand the cause for concern, there was no option of "take it to your car" or similar, just simple confiscation. I also was denied retrieval of the key later that same day.