Mishneh Torah, The Sanhedrin and the Penalties within Their Jurisdiction 26:7משנה תורה, הלכות סנהדרין והעונשין המסורין להם כ״ו:ז׳
When any person has a judgment adjudicated by gentile judges and their courts, he is considered a wicked person. It is as if he disgraced, blasphemed, and lifted up his hand against the Torah of Moses our teacher. This applies even if their laws are the same as the laws of the Jewish people. This is indicated by Exodus 21:1: "These are the judgments that you shall place before them." "Before them" and not before gentiles; "before them" and not before ordinary people.
The following procedure should be carried out if the gentiles have a powerful law enforcement system and the opposing litigant is a stubborn and powerful person from whom one cannot expropriate property through the judicial system of the Jewish people. One should summon him before the Jewish judges first. If he did not desire to come, one may receive license from the court and salvage one's property from the litigant by having the case tried in a gentile court.
The following procedure should be carried out if the gentiles have a powerful law enforcement system and the opposing litigant is a stubborn and powerful person from whom one cannot expropriate property through the judicial system of the Jewish people. One should summon him before the Jewish judges first. If he did not desire to come, one may receive license from the court and salvage one's property from the litigant by having the case tried in a gentile court.
Shulchan Arukh, Choshen Mishpat 26:1שולחן ערוך, חושן משפט כ״ו:א׳
It is forbidden to appear for trial before heathen Judges and in their Courts of Law, i.e., [the locality wherein] permanent judicial sessions are held by the [civil] magistrates, even regarding a lawsuit that they [the heathen Judges] adjudicate like the Israelite Law. Even if the two litigants agreed to be tried before them, it is forbidden. And whosoever appears for trial before them is considered a wicked person and is as though he blashphemed, reproached and rebelled against the Law of Moses. Gloss: The [Israelite] Court of Law has the authority to pronounce against him the less severe [Niddui] and [even] the more severe [Herem] ban until he suspends the [legal] rights [which he delegated to] the heathen [authorities] from upon his fellow [-litigant]. Likewise, is the ban pronounced against him who strengthens the hand[s] of the one who goes to law before a heathen [Court]. And even if he does not go to law before a heathen [Court] but compels him [his adversary] by means of a heathen [Court] to appear with him for trial [before] a Jewish [Court of Law], — he is fit to be laid out on the post [for a flogging]. , infra § 388. One who resorted to heathen Courts and was pronounced guilty by their laws, and then he [the guilty person] summoned him [his fellow-litigant] again before Israelite Judges, — some say that we do not attend to his [case]; while others say that we do attend to his [case] unless he was the cause of a loss to his fellow-litigant before the heathen [Courts]. However, the former opinion seems to me to be fundamental.
Shulchan Arukh, Choshen Mishpat 26:2שולחן ערוך, חושן משפט כ״ו:ב׳
[If] the hand of the heathen [Judges] was powerful, and his fellow-litigant is a stern individual [refusing to appear for trial in a Jewish Court] and he [the claimant] cannot retrieve [his claim] from him through Israelite Judges, — [then] he should summon him [the recalcitrant defendant] before Israelite Judges first. If he refuses to appear, — [then] he obtains permission from the [Jewish] Court of Law and retrieves [his claim] through heathen Courts from the hand of his fellow-litigant. Gloss: The [members of the Jewish] Court of Law have the right to go before the heathen [Courts] and bear testimony that this party is guilty to that party. This entire [ruling is applicable] only when [the recalcitrant person] refuses to heed the [Jewish Court of] Law, but otherwise the [Jewish] Court of Law is forbidden to give [one] permission to appear for trial before a heathen [Court].
Me'irat Einayim on Shulchan Arukh, Choshen Mishpat 26:8מאירת עיניים על שולחן ערוך חושן משפט כ״ו:ח׳
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Bava Kamma 92b:14בבא קמא צ״ב ב:י״ד
Rava said to Rabba bar Mari: From where is this matter derived whereby people say: If you called to your friend and he did not answer you, throw a large wall and cast it at him, i.e., do not attempt to help him anymore? Rabba bar Mari said to him that the source is as it is written: “Because I have purged you and you were not purged, you shall not be purged from your impurity anymore, until I have satisfied My fury upon you” (Ezekiel 24:13).