Yeah, the NHL and PA could be in court for years. The PA might win some cases causing precedents other leagues would be p.o.'d with the NHL for creating.
I don't even know if the NLRB in the US could force a cap if things went the impasse route. The NLRB still can't really impose provisions that would be illegal under anti-trust law or some some restrictive marketplace laws. Of course bureaucrats do what they want until you take them to court.
Heck. People cite the football experience, the NFL union never put up much of a fight. And they aren't international. In basketball, the union agreed to it.
Canada and the US have a free trade agreement only, it isn't a full economic union with bilateral labour arrangements. In Canada, Canadian labour codes apply. The NLRB decisions might prove to be toast in Canada, if the NHLPA fights it.
The NHL needs the PA's signature to impose a cap in the US I believe; otherwise why wouldn't they just agree to it amongst themselves. Perhaps the reason the NHL is going the CBA route for a cap is because of the anti-trust laws or to circumvent restriction of trade or free marketplace rules? And then they would go to the NLRB to circumvent the union that won't sign to allow the NHL to circumvent the Sherman Act? Uh huh. I don't get it. I'd need Tom Benjamin to explain all this to me..
The NHLPA could play the Canadian card if things got that far. Gee, we are not even beyond Betman's drop-dead date for league closure, yet.