From her early days writing a book on Civil Procedure in Sweden, to her time as law professor, judge, and justice, Ruth Bader Ginsburg was always acutely sensitive to the fact that legal systems are not hermetically sealed from each other. Always there must be ways of negotiating the interactions among such systems. In the United States, of course, such interactions often involve navigating a federalist structure of fifty-one different sovereignties, in addition to tribal governments.