It really should be a 500 error, not a 400.
Edit: Listen, USA, it's not so difficult, and we all really need to stop siphoning off everyone's data like it's no big deal, laws or not. I wrote some stuff for the GDPR, just had to remove some emails from our database, and honestly, we shouldn't have been collecting them in the first place and neither should you. This surveillance capitalism we're all building is not a good thing and you should not be complicit in it.