Incidental question

In the Roman conflict of laws, an incidental question is a legal issue that arises in connection with the major cause of action in a lawsuit. The forum court will have already decided that it has jurisdiction to hear the case (resolving any issue relating to forum shopping) and will be working through the next two stages of the conflict process, namely: characterisation and choice of law. For example, the court may classify the cause as "succession", but it notes that the plaintiff brings the claim for relief as the deceased's widow. Before the court can adjudicate on the main issue, it must first decide whether the plaintiff actually has the status claimed, i.e. the incidental question would be the validity of the claimed marriage. The inconvenient reality is that many lawsuits involve a number of interdependent legal issues. In purely domestic cases, this poses no difficulty because a judge will freely move from one domestic law to another to resolve the dispute. But in a conflict case, the question is whether the incidental question is resolved by reference either to its own choice of law rules, or to the same law that governs the main issue (the lex causae). States have not formulated a consistent answer to this question.

For an incidental question to arise, the forum court must have applied its characterisation rules to determine that:

Suppose that a French court hears the case of an American national who dies domiciled in California leaving movables in England. The French choice of law rule would refer the distribution of personal property to California law which has community property provisions entitling his widow to share in his estate. The marriage was in England and, as both the lex loci celebrationis and the lex situs, English law declares it valid even though it is void ab initio under California law because it is considered bigamous (see nullity): a divorce decree granted by the Arcadian courts was recognised as valid in England, but not in California. Should the widow's claim be determined by the English or California law? There are different views:

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