I'm not so sure
Technically, unless he has a visa or residency in the US, he does not have the right to put on an exhibition in Las Vegas if he is Norwegian.
I would have thought he'd need a CW-1 Temporary Work Permit at the very least.
The fact he's got through border control in Las Vegas does not mean he had any rights to do any work. Chances are that he travelled on ESTA. Travelling to put on an event would not be classified as business either, as he's doing actual work in the US. Business travel allows you to attend an event as a visitor, not to actually do any meaningful work.
Biting the hand that feeds IT
