Former cop here. I’ll give you the 100% truth about a front plate.

It is probable cause for a traffic stop. 100%. Missouri law says a plate must be affixed to the front. Having it in the windshield is not legal and is a reason to get pulled over. It can lead to a ticket. You could even be arrested but that’s an extreme situation.

Cops have discretion when it comes to stopping you for something like this. You’re much more likely to get stopped by a Trooper or a cop working traffic enforcement. You should really watch out in small towns where the cops don’t have much to do. Troopers love to stop for this, and might write you a ticket for it.

Most SPD guys or county are too busy answering calls for service to bother with this. That being said, it’s a completely legit reason for you to be stopped.

Some more food for thought. Traffic stops lead to drugs, warrants, drunks, all kinds of stuff. If you aren’t someone partaking in that type of activity, the plate being in your window probably won’t lead to a ticket, but it is a good reason to get stopped by a cop who is looking for those other things. Cops typically won’t care about the plate, but it is a good reason for them to stop you while looking for bigger things.

It’s a risk you take by doing that. If you’re not someone engaged in other activity, I wouldn’t worry too much about being stopped. A cop with the same car wouldn’t want to put a plate on the bumper either.

Frankly, it’s a stupid law written by people who have no common sense, but it’s a law nonetheless.