How do i make a area demilitarized?

So im just making a mod for Canada cuz I feel like making a focus for them and im trying to find how to make Quebec demilitarized at the beginning of the game. TY if you can help btw.

You will need to copy Quebec's state folder to your mod's folder if you haven't changed the countries which have cores on/control the state. If this is in your Canadian Expansion mod, for example, then you don't need to do this, as the country Quebec has been assigned the states.

If you navigate the folders of your mod to history -> states, and open the file 466-Quebec, you will need to add "set_demilitarized_zone = yes" inside the history section.

See how Germany's Rhineland does it: