If he's playing for the reserves, then surely that means he has some kind of official status at Pools?
I mean you can't just throw players into cup ties (right, Bury? ), even Pontins ones, without registration, can you?

I think trialists can play for the reserves without registration. dunno about reserve cup ties though.

As far as I am aware he can play as an unregisrered played as at trialist or as a registed player but on a non/contract basis.