According to our Gemara, legal documents and contracts that are written in arka’ot shel goyim – in non-Jewish courts – can be relied upon, with the exception of giṭṭin, and shihrurei avadim (documents freeing slaves from their masters).
The origin of the term arka’ot appears to be from the same Greek word that gives us the English word “archives,” meaning the place of the judge or the place of the ruling authority. In the context of the Talmud it is used to mean an official non-Jewish court, as distinguished from a traditional beit din.
Under ordinary circumstances, Jews were actively discouraged from making use of arka’ot shel goyim. Rashi explains that they are accepted as reliable with regard to contracts through the mechanism of dina d’malkhuta dina – that the law of the land is considered binding as law. Some suggest that Rashi believes that non-Jewish testimony is acceptable according to Jewish law, with the only problem being that we fear that the non-Jew may tell a lie. If, however, the non-Jewish legal system accepts someone’s testimony then it can be relied upon. According to Tosafot, however, documents approved by a non-Jewish court are acceptable only on a rabbinic level. The Rosh explains that this was a takanat ha-shuk – an enactment established for the good of the marketplace. Since Jews needed to rely upon such contracts, the sages established ways to accomplish that so that business people would not suffer financial loss. The Talmud Yerushalmi explains similarly that this allowance is made for the benefit of Jews who are borrowers and lender.
These explanations are not relevant to the laws of divorces, since non-Jews play no role in Jewish divorce and therefore cannot be relied upon for testimony in that case. Rashi explains that shihrurei avadim fall into the same category simply because the rules of giṭṭin and shihrurei avadim generally parallel one another.