Unless you are a better labor attorney than, well, a labor attorney, then I'll take his word for it. I called him up to ask. Was on the phone with him as I read your response.
He said, "It depends on the contract."
It's even more localized than I thought and more restrictive than you think. The company doesn't always get to decide, and here they don't. We get a vote. Period.
Last time, 5 people who signed cards changed over and the Union lost for the second year running. But only at the vote.
Well, you must not be explaining the issue to your FIL properly or he is mistaken. Given that his response is that "it depends on the contract" I presume you aren't explaining it properly. Given that a recognition of a union (either through card check or election) precedes a contract, it is silly to say it depends on the contract. Unless, your FIL is talking about neutrality agreements.
What I am talking about is the initial decision to have a union form. As a matter of federal labor law an employer, when presented with 50%+1 of signed authorization cards, can either choose to recognize the union or force an NLRB election. The company always get to decide. Period.