I work at a Native American Casino and they are going to post all of our salaries in the tribal newsletter is this legal???? If not were can I find some information on it to stop it before it happens.

As you are working for a tribal organization, I would check the laws they have. Many US employment laws do not apply.

There is nothing in US employment law that would prohibit you publishing yur salaries on a billboard on the highway if you wanted. It may not be a good idea, but it is legal.