Thank you for making the owner's case for them. The NFL's charge before the NLRB is that union bargained in bad faith all along, with no actual interest in getting a deal done and instead preferring litigation. If the NLRB agrees with you, this will potentially undo the NFL's decertification and put the union in a significantly disadvantageous position, staring up at a lockout that they have no recourse to end beyond bargaining.
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The key distinction is that from the NLRB's perspective, lockouts are legitimate. They're identical to strikes, except they're perpetrated by management and not labor. But there's nothing a priori unacceptable about a lockout, since one can always be avoided (and ended) by negotiating and it's the NLRB's goal to encourage such. The NLRB, however, has a vested interest in preventing sham-decertification-coupled-with-lawsuit as a negotiating practice since it is an inherently unfair negotiating strategy (and it ties up federal courts with an issue that should really just be resolved in a board room).
In principle, if a union should be allowed to strike then management should be allowed to lock out labor. If one isn't allowable, then the other shouldn't be either.
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LIFE IS ABOUT CHAMPIONSHIPS; I JUST REALIZED THIS. The MILWAUKEE BUCKS have won the same number of championships over the past 50 years as the Green Bay Packers. Ten years from now, who will have more championships, and who will be the fart in the wind ?