The replacement player scenario would likely begin with the league declaring a negotiating impasse - a claim that its dispute with the players cannot be resolved through collective bargaining. It could then impose new terms of employment without consulting the NHL Players' Association.
The Players' Association would almost certainly challenge that move by filing a complaint with the National Labor Relations Board in the United States. That would begin a process of appeals and hearings that could take months, to determine whether the NHL has negotiated in good faith throughout the dispute.
If the NLRB rules in favour of the Players' Association, the two sides would return to bargaining. If it rules in favor of the NHL, the league would have the right to impose its last, best collective bargaining offer and open for business under those terms.
After losing the appeal, the players could go on strike. Another option for the NHLPA would be to decertify - cease to exist - leaving individual to decide whether to return to the NHL. Former NHLPA members could then attempt to sue the NHL under anti-trust laws, particularly if salaries took a big hit under the new arrangement.
Under either scenario, the league could try to use non-NHLers as replacement players. But Quebec and British Columbia do not allow replacement workers in most circumstances. Also, Canada and U.S. laws forbid the use of replacement workers from outside the country, which could leave U.S. teams restricted to using American players and Canadian teams restricted to Canadian players. And could those players cross borders to play games?
Under any circumstance, some NHL players would likely go back to work, but how many? Where would the rest of the players come from? The American Hockey League? Is it in the interest of NHL teams to debase the minor-league product by raiding AHL rosters?
What if the Players' Association set up picket lines outside NHL arenas? Would arena staff cross the line?
Would fans pay to see a replacement league? At what price? Are they willing to cross a picket line?
Would sponsors and broadcasters get on board? Without them, the NHL is legless. What TV network wants to be accused of supporting scab labor? What retailer wants to link its product to a potentially disastrous scheme?
On the other hand, a replacement-player league need only be a modest success to achieve its purpose. If a few fans make the leap, a little cash is generated and the illusion of NHL-life-as-usual can be propped up for a few weeks, how long will the average NHLPA member stand by and watch before he picks up the phone?