the local forms, decide to create a marriage either by a simple public exchange of vows (per verbis inter praesentes), or by habit and repute. Because the need for conformity between states requires respect for the legal systems, it is now very difficult to identify states with no local system for the celebration and registration of marriages, and even more difficult for the courts of one state to justify a decision to support the prejudices of two of its citizens against the laws of the second state. However, other states permit informal marriages to acquire legal status and, where this happens, there is no reason in principle why international recognition should not follow. Government registration In some countries, the registration of a marriage means that it cannot later be declared invalid, since it has been accepted by the government. In Taiwan, which follows a variation of the Napoleonic Code (received by way of Japan), the presumption is that each country maintains a central registry of its citizens, including their marital status. If a Taiwan citizen marries in another country, however, this information may not find its way into the records. Many thousands of ROC soldiers who came to Taiwan in 1949 left behind wives in mainland China, but married local Taiwanese women. Since the two polities did not share records, the result was a pattern of legally recognized second marriages, despite the ban on polygamy by both sides of the Taiwan Strait. Today, foreigners wishing to marry Taiwan citizens must present letters from their countries' representative offices testifying that they are not already married. (Of course a determined bigamist might marry in some third country.) In the case of countries which lack centralized family records (such as the USA), a notarized affidavit is accepted. The age of marriage Different minimum age requirements also can lead to problems in mutual recognition of marriages. A marriage of young children is in some countries deemed to be against the public order, minimum ages for recognition are sometimes set (which may vary from the minimum ages for marriage itself). For example, in the United Kingdom, the Immigration Rules 1986 were introduced to bar persons under the age of 16 from entering the UK in reliance upon their status as a spouse. Nevertheless, for other purposes, such marriages will be recognized as valid so long as the parties had the relevant capacity under their personal