It's not an issue of authority alone. The ICL has a very intrusive schedule, interfering with multiple international events. Any player you'd expect in the ICL, with no ban, would turn it down because he's more keen on playing for his country.
Cricket New Zealand was hit by a players' revolt over pay hike, when they were paid little. One of them, Chris Drum, left the game because he thought he'd earn more from a job as a travel agent than by playing cricket. In fact, all the ICL players whom many consider good enough for their national teams, have issues with their respective boards and joined it in protest. Nobody who's having a good time and values the national cap will join the ICL.
The very appearance and image of the ICL is about sloganeering and lobbying. All their advertisements try to brag and challenge the authorities, without presenting anything definite. In comparison, the IPL only shows what is happening. Even in commentary, we find that the IPL commentators only talk cricket and something off-topic, for a lighter moment- and if anything is left, they try to promote themselves, while ICL commentators do far too much self-promotion. They're forced to do that when they're struggling, and that league isn't getting any attention at all, when (source : TAM) international matches often get TRPs of 8 units and the IPL gets 5 or 6, the ICL gets a paltry 2 and a half.
Why would anyone join such a league? Least of all when its credentials are so dubious? Even though it is banned, they should have tried harder, and done a Packer with his WSC. They couldn't do a thing.