unfazed you always could use a gps in the enroute section but just in Lat and Long mode. You couldn't use it for direct to a beacon.
I believe they are now allowed to use the goto function during the airways bit as well as in the hold.
The instrument procedures are still flown with primary navaids only.
Can you not just pull the GPS antenna input and tech it so your stud just has to jump through the usual hoops?