Jury Nullification?
Rumors to the contrary, we do have a right to free speech, so you can say anything you want in a courtroom without being arrested, unless it causes immeidate danger (e.g. yelling "FIRE!").
When jury selection happens, I have heard that you can be rejected from being on the jury if you say (essentially) that you don't agree with the law. Not agreeing with the law is precisely what leads to jury nullification.
"F@$% you, your honor!”
“Bailiff, please arrest mr. nthj for contempt of court”
So, saying you'll be arrested for talking about jury nullification in court doesn't really give an accurate picture. Though it is probably technically true.
I think that they aren't medieval precisely because we have trial by jury, jury nullification, etc.
I would expect trials in non-common-law countries to feel much more medieval.