국제계약의 적용법규로는 통일법을 비롯하여 통일규칙 및 국제사법이 있지만, 오늘날 동 분야의 다양성과 각국의 사정 등으로 인하여 국제사법에 의한 법적규제가 가장 원칙적이고 일반적인 법적 규제의 방법으로 인정되고 있다. 국제계약상 적용법규의 결정에 관한 문제에서는 통상적인 상사매매계약에서 명시적인 준거법 약관이 존재할 때에는 당사자에 의한 법 선택이 인정된다. 만일 계약 당사자에 의하여 적용법규가 선택될 경우에는 당해 계약 또는 계약 당사자와 어느 정도 실질적인 관련을 가지는 국가의 법률이 아니면 부인될 수도 있고, 계약에서 발생하는 복수의 쟁점에 관하여는 각기 다른 법률을 적용할 수도 있으며, 계약 체결 후 사정의 변경에 의하여 준거법이 변경될 수 있다. 그런데 소비자계약을 비롯하여 근로계약이나 대리점계약 등과 같이 당사자 간에 지속적인 계약관계를 유지하는 경우에는 당사자가 선택한 법규에 대하여 일정한 제한을 가할 수 있는데, 이에 관하여는 기능적 공공질서론과 특별연결 이론에 의한 해결이 보다 합리적이고 타당하다고 본다.
A problem about selection of the application legislation is most basic and important problem to contract international contract. There are uniform law and private international law that person concerned can claim including unity law to application legislation of international contract. International contract field is such unific law but field that treaty is formed is limited, and even if there is unity law, because the all countries are not ratifying this. the usefulness of method that control international contract by unity law is limited. Therefore, method of most topical and general legal regulation about international contract is depending on legal regulation by private international law today. To decide application legislation of international contract, in case clear stationery is included in agreement when contract general sales contract. it is usual that law that person concerned selects is approved. That is, in case international contract is contracted by agreement what clear stationery is included, appointed law is applied by person concerned in principle. If agreement is selected by improper means or mistake, the effect is denied. Effect can be denied agreement of coincidence contract. In case of application legislation is selected by person concerned, can be denied if law of the country that have person concerned and in some degree real connection is not. Person concerned applies each other law about many point at issue that happen when contract. After contract conclusion, if assessment is changed, application legislation can be changed. By the way, in case must preserve contract relation between person concerned like labor contract or consumer contract, on contract to protect feeble jar, the country inflicts fixed limitation about person concerned’s law selection. Specially, there is that become an issue here in case injure law purpose of the country that result that apply law that person concerned of contract selects has contract or person concerned and real connection. About this, method of construction theory that arrange through precedent, public order theory, functional public order theory, special connection theory, Rome treaty are supplying clue of the solution. At time that person concerned’s law selection consists by improper means such as mistake or malice and duress, because can not speak that there was appointment of authority cited law by a genuine doctor of person concerned, these law selection is unrecognized that is valid. About this, mutual agreement about international jurisdiction that mark country’s court that other person of contract belongs to competent court in remarkably irrational and unfair case the jurisdiction sum of that is nullity insist. In case the country is intervening in contract relation by forcing legislation in labor contract, such forcing legislation is a person who insist that law selection by person concerned is excluded unlike legislation ordinary administration of justice enemy because is regulation method of construction enemy. About this, a certain person talking law selection by person concerned that is valid in principle in field that is controlled by forcing legislation with labor contract, insist that must apply forcing legislation by public order exceptionally. Because regulation about public order excludes application of appointed authority cited law according to principle of private international law exceptionally, the abuse is analyzed that must take care strictly. Therefore, because possibility that application of a law that person concerned selects in public order theory is excluded must be limited extremely, method that person concerned selects is applied just as it is, and law purpose for worker protection is infringed. Theory that is going to supplement limit of these public order theory is functional public order theory. According to functional public order loan, active practical use of regulation and application of the third departments' forcing legislation about public order are possible, and can correct limit by public order theory fair degree. Special connection theory is theory that is going to secure application of the third departments’ forcing regs that have contract relation and real relation through special connection. If see from these viewpoint, regulation of Rome treaty is observed as that establish special connection theory as practical law.