Well I actually read the article and it doesn't say the PFA are "threatening" anything, This is what the useless PFA CEO actually said:
"I feel like we've reached a stage where people are ready to take legal action, where people are ready to take tangible action on the pitch to try to resolve it, because it's a sad state of affairs. I think it's a defeat for football when the players need to take the justice in their own hands because they don't feel protected."
A lot of thinking and feeling, not much threatening. Still, Harris got his headline. The tosser.
And, while I am at it, I see everyone is against the new CWC now that Liverpool and United aren't in the thing.