John:
The devil's in the detail
I was referring to FAA rules, and specifically the example I quoted. The "student" in the right seat, (in the case of the jetranger), does NOT hold ANY pilot certificate, and the "instructor" was NOT a rated CFI, therefore, holding ONLY a pilot license he was obligated to fly from the right seat. This is NOT a two pilot crew situation.
Can you imagine the insurance nightmare if something had gone wrong and he was in the "other" seat with no CFI license?