In your export_descr_buildings.txt file, search for Mailed Knights. Once you have found them, you should see something like this:
Code:
recruit_pool "Mailed Knights" 1 0.2 2 0 requires factions { england, scotland, france, hre, spain, portugal, milan, venice, papal_states, sicily, }
To make them unable to be recruited after gunpowder is discovered, simply add this to the end of the recruitment line:
Code:
and not event_counter gunpowder_discovered 1
The final code should look like:
Code:
recruit_pool "Mailed Knights" 1 0.2 2 0 requires factions { england, scotland, france, hre, spain, portugal, milan, venice, papal_states, sicily, } and not event_counter gunpowder_discovered 1
Do that for all Mailed Knights entries, and you're done! For a more in-depth analysis of the export_descr_buildings file, look here.