Is The trope that wizards can't use armor just an arbitrary limitation?

[alexondria]

Originally Posted by mindstalk

A sufficiently powerful magician should have invulnerable skin anyway and thus not need armor. :) Like Monkey in Journey to the West.

If you are using Monkey as an example he did have some very nice armor along with that nasty staff.

As a side note I think he's looking for pre D&D fantasy that says wizards can't wear armor. Take the Merlin example that's been offered up as a wizard that doesn't wear armor. Nothing I've read in the stories says he can't wear armor, he's just never described as doing so. Maybe it's because he can't (either due to it inhibiting magic or he just never learned how to properly wear it), maybe it's a trait of his position as adviser not warrior, maybe it's a fashion choice. The writers seem to have not thought it important enough to say.