The answer to this is to get rid of the option altogether.  If you want someone out of your territory, go and kill them.

Had this happen in FE.  Unit got trapped.  I did report it.

What's really annoying is when the AI is hell bent on crossing your lands with pioneers and you have to repeatedly tell the idiot to get out of your lands every. single. turn. Well, until you just sick of it and either:

a) declare war and lay waste to them, starting with the pioneer or

sigh heavily and just let the Pioneer through and watch them settle/outpost in your backyard

I dunno, how about players cannot enter a players territory for 3-5 turns after being told to get out and the other player agrees, unless war is declared or open borders treaty is agreed upon.

I had this problem in a earlier version of FE (Not Legendary Heroes). Definite fix needed here. 

Maybe it has to do with the fact that the tiles you standing on are not blocked as they should be? You should not be able to stand on a tile that you can't stand on in the first place when you are kicked out of another persons territory.