The main obstacle is the will to enforce the law.
In the Silicon Valley wage suppression cartel, there were tons of evidence, including evidence that indicated intent, and awareness of the illegality.
Eric Schmidt, Google CEO, even wrote stuff like:
> I would prefer that Omid do it verbally since I don’t want to create a paper trail over which we can be sued later?
All they got was a measly fine.
Obama DOJ had no will to criminally prosecute even with ample evidence.