using a sword as a warrior of the order

Even though you are supposed to use a staff as a warrior of the order, what is stopping you from using a sword?
will the game not let you equip it? or can you not use magic with a sword equipped?

Nothing stops you from using one, but it could be hard to find trainers unless you unlocked some in the bandit camp before joining the Monastery.

training a weapon is a waste of your LP… until the very end that is..
First max out str, then and only then consider putting points…
The vast majority of the game, swords are the best weapon you can have… but the ultimate weapon is a hammer that is considered an Axe… and gives +6, so a skill of 4 in axes is max you should ever need.
Oh, it is a one handed axe that allows a shield in other hand and swings like a one handed sword…