For information not provided in the OP
http://abcnews.go.com/politics/t/blogEntry?id=16364003In a nutshell, the act has been approved twice in 18 years. The native American objection is in the senate bill, the bill the WH approves grants tribal courts the ability to try the cases. The House version is the old bill which leaves the process to the federal courts. Repubs feel the addition is unconstitutional.