@maxdancona,
The only legal rights the players have are those afforded to them by their individual and collective contracts.
I've no problem with the matter being resolved through negotiation or in court. What I do have a problem with is how this is being described as a "free speech" issue. It simply is not.
If the players have any "right" to ignore the directions of their employers it is because their employers granted them such a right through contract. If that's the case, shame on the employers.
The league has botched this matter since the beginning and as a result, they are losing viewership and revenue. If they have calculated that eventually, it will blow over, they are mistaken. I know people who are huge football fans who now refuse to watch the games.
The negative reaction to "take a knee" isn't, in the main, based on antipathy for BLM, although given the past antics of that organization, it would not be surprising if it were. The primary issue is the politicization of sports, a pastime in which Americans seek refuge from the chaos of everyday life.
The players have a great many other ways available to them to register their views on the subject. I see no evidence whatsoever that these demonstrations are having any sort of positive impact.
If as you say, the players have the upper hand, then it's all the more reason why Nike's ad campaign is a sham and Kaepernick is nothing like a hero.