Now, understand that "tribal rights" aren't really rights. They are routinely violated. They're really a description of debts owed by the U.S. government to certain groups of its victims, and the government will do anything it can to skip out on those debts. Politicians don't care if they kill people. But of course, when you make it harder for people to get health care, that kills some of them. Which is an act of genocide.
Of particular concern is the work requirement itself, because the unemployment rate on reservations runs over 90% in some tribes. There are no jobs on some reservations. So how exactly are "able-bodied adults" supposed to work if there is no employment within reach? The government doesn't care about that, and it doesn't have to. The same applies in many poor areas, but it is worst on the reservations, which are the poorest parts of the continent, which is not an accident.