It strikes me as odd that this would be decided by some random immigration official at the border. Surely, you'd chip away at getting an appropriate visa at the US embassy back home? Or are there in fact two possible points of failure?
For Canadians and Mexicans there is a different visa, called the TN, created under NAFTA. If you read the NAFTA proceedings, you'll come to understand that the method of getting verified at the border was meant to make it easier and quicker to get a Visa, for certain classes of professional. The one professional category involving computers, 'computer systems analyst', was so vaguely defined that one could only interpret it was meant as an umbrella term.
But what's happened in reality is that small-minded border guards have been given the authority to simply reject people. They demand all sorts of things that aren't in the law, and they make no apologies.
US law doesn't ban individuals from being international actors. It barely even acknowledges the possibility. But ultimately you're subject to the whims of whichever boarder guard your happen to meet.
Canadians are legally allowed to vacation in the USA for up to 6 months. I'm not sure, but I don't think the law is too specific on not being able to work (the semantics of the word are too tricky), but you need a visa to be in someone's employ. That may leave certain possibilities open.