Tribes and the unions that represent casino workers have been at loggerheads for years over the right of union organizers to even enter onto Indian land. The few federal courts that have looked at the issue have decided in favor of the unions. Here’s my write-up of the first major case: https://www.gamblingandthelaw.com/column/court-rules-tribal-casino-is-merely-a-casino/
The House of Representatives passed a bill a few days ago that would take away the unions’ right to easily organize workers at tribal casinos. H.R. 986, the “Tribal Labor Sovereignty Act of 2017,” introduced by Republican Congressman Todd Rokita, would take away the power of the NLRB to regulate labor issues on Indian land. The bill passed 239-173, with only 14 Democrats voting in favor. The government shutdown has momentarily stalled the bill in the Senate.
Interestingly, Rokita was the largest recipient of Indian gambling campaign contributions in the House in 2017, even though there are no tribal casinos in his Indiana district. He has announced he is running for US Senate.