David Treuer, an American Indian, is writing a series of dispatches for Slate in which he visits Indian casinos. I'd never heard the story of how casinos on Indian lands came to be. It seems a state tax bill on a mobile home led to a lawsuit which led to a legal precedent that state and federal governments have no regulatory jurisdiction on Indian lands.
The Supreme Court ruling in the Bryan case was expansive. More than just a ruling on taxation, it declared that states and the feds had the right to police the reservation only in the interest of "law and order" and had no civil or regulatory jurisdiction over sovereign Indian nations. Until this time, tribes and states more or less assumed that states had civil and regulatory power on reservations. But the Supreme Court maintained that as sovereign nations, Indian tribes had always had the right to govern themselves (including civil and regulatory powers), just as all nations do, and that tribes should deal with the U.S. federal government, not with states. Kansas, for example, has no power to levy taxes in Luxembourg -- and not only because Luxembourg is far away.