Page "State court (United States)" Paragraph 25

In civil cases, all or some of the substantive law issues decided by a state court may be determined under the law of another state or country, if that state's choice of law rules provide for the application of another state's laws.

For example, if someone sued a resident of Missouri in a Missouri state court for an automobile accident arising in France because it was not possible to obtain jurisdiction over the defendant in a French court for some reason, the Missouri state court might apply the French law applicable to lawsuits arising from automobile accidents.

Similarly, a Missouri state court presented with a Last Will and Testament signed in Florida, might apply Florida law rather than Missouri law to determine if the document was signed with the proper formalities.