Frequently referred to as customary law, the unique traditions and customs of different Native American tribes are cited by their tribal courts as authoritative and binding law. The recent use of customary law as a mechanism for deciding individual cases is not uniform among tribal court systems as it differs depending upon which tribe's judges are working to place custom into contemporary judicial analysis. Understanding the present role of customary law in tribal law requires first understanding the nature of customary law and then understanding how it is being used. The effect of customary law is dependent upon the place it has in relation to other sources of law from tribal statutes to state common-law. Furthermore, the differing treatment afforded customary law by separate tribal court systems in many ways is a reflection of the degrees of proof required by different courts to establish what is or is not a tribal custom.