When someone doesn't know basic felling technique, it needs to be taught to them.
They needs to know the language.
Teach him in private. Applaud him in public, after he understands his job is on the line, same as if he was driving a vehicle from the passenger seat, or any other reckless bs
You can find a replacement-liability like that guy, anywhere.
You can always find desperate guys willing to work dangerously.
Barber chairing a tree can kill him, pull down a power line killing someone else, etc, etc.
Rookie nonsense.
If he doesn't want to follow SOP, start with a suspension if he's got 20 years at the company. If he's got 20 years of being a rookie feller, he has almost certainly got other dangerous habits. If he's not having 20 years in at your company, and uncooperative, adios.