The application of national law to international and regional disputes has become increasingly common in recent years. The principle that international and national law apply equally in these cases has been upheld by the United Nations and many other international bodies. ICSID tribunals have also concluded that national laws should be applied in such cases. However, there are a few notable exceptions. For example, a case in which a foreign national has claimed that they are the victim of human trafficking may be subject to international law.

The process by which courts decide whether an international law is international or national is called the rule of recognition. The term is an independent concept and has no relationship to the concept of national law. The second criterion is the acceptance of the secondary rule by the legal profession, which differs from that of judges and officials. This acceptance can be determined by studying how the legal profession invokes the primary rules. It is important to note that there are a number of exceptions to this requirement.

As such, a national court may not be obligated to interpret international law in a specific case. A nation may voluntarily agree to apply its national law, which may be a matter of national interest. In these cases, it is the responsibility of the parties to agree on the appropriate legal system. A treaty arbitration award is also governed by the proper law of the contract, not the national courts. It is therefore critical that courts make decisions on interpretation of international and national law when they determine the validity of a contract.