My husband is a 62 year old Canadian. He was contracted by a Canadian company to go to Detroit to monitor a Canadian registered aircraft while it is being maintained by a USA company. He has been rejected entry to the USA. They harassed him, finger printed and patted him down. Their claim is that he is taking a USA job. He was hired by a Canadian company and paid by them. He is helping them bring business to the USA. Can they reject his entry? How do we fix this? We cannot cross even to attend church now without a hassle. We cannot afford a lawyer to fight this. We filed a complaint but this only aggravated the NAFTA agent more.
There's a crucial difference between being contracted by a Canadian company and being hired (as an employee) by a Canadian company.
An employee of a foreign company who goes to the US as a representative of that company to see to their interests there, in a manner integral to the foreign company's business outside the US, is allowed to do so on a business visa (or whatever the correct formality for a Canadian national in lieu of a visa is), since the Matter of Hira decision from 1966.
However, if your husband is a contractor, then all of that doesn't apply. As a contractor he counts as a "company unto himself", and what he's proposing to do would amount to setting up shop in the US for his one-man company, and there producing a service that he happens to sell to a Canadian customer. That means he needs have a work permit for being self-employed, which is probably not going to be easy (there doesn't seem to be any visa categories that obviously apply to that situation).
(The reasoning behind this distinction is that it is thought reasonable for a foreign company to want one of their own trusted people to be the one who takes care of their business interests -- but if they don't have one of their own available and are willing to have their interests represented by an outside consultant instead, they ought to be as happy to contract with an American stranger as they are to contract with a Canadian stranger).