If he was flying illegally, he was flying as pilot in command illegally. But still pilot in commend.
Though it makes sense, a friend of mine had a different experience.
He was "checking out" the new owner of an aircraft he'd just bought that day (which I had delivered the day before). My friend and the new owner flew all over that day, with my friend mostly sitting and speaking the occasional bit of guidance, but not actually flying. The bit they both missed was to check the fuel, 'cause they ran out and crashed - wrecked the plane, but not really hurt. Bad on both of them...
Turns out that the new owner did not have a valid license, but my friend did. My friend received the charge for the breach of regulation associated with running out of gas. He was the only licensed pilot aboard, and even though he was not flying, and not the PIC of record at the beginning of the flight, the government deemed him to be so at the end!
The accident should not have happened, and my friend missed the mark, but he was surprised to receive the formal punishment as PIC, when no one thought that he was PIC during the flight.
So, if you're a pilot, and you're just riding along: Actively prevent accidents and offenses, and, attempt to confirm (within the bounds of courteous behaviour) that the other pilot, is legal to be PIC!