Rambam (Hilchot Melachim ch. 4) says that there is ddm in EY and it is even a capital offense to be over even for minor infractions such as disobeying an order to turn in a certain direction or violating house arrest (ibid Halacha 5). The Shulchan Aruch (Choshen Mishpat 369:6) decides accroding to Rambam and aparently Rashbam (Baba Batra 54a d”h veha’amar Shmuel), who holds that thereason is that all of the residents implicitly agree to obey the law. According to Rav Ovadia one cannot say kim li against both Rambam and the Shulchan Aruch and therefore one is obliged to pay taxes to the State (Yechaveh Daat 5:63).The Ran (Derasha 11) admits that there is ddm in EY regarding laws enacted for public order and safety.
So far as commercial law is concerned, while we do not say ddm batei din will pasken the civil law as minhag hamedina. Of course, one must go to the bet din, which will decide how to apply the secular law.
Rav Moshe’s ruling is limited to an instance where the criminal is non-violent (see Rema Choshen Mishpat 388:7 and see 388:12 regading financial crimes, Schach Choshen Mishpat 388:45 and Tzitz Eliezer 19:52) and the reporter is not obligated by law to report the crime (see Bet Yosef (see Baba Metzia 83b-84a and Bet Yosef, citing the Responsum of the Rashba, Hoshen Mishpat 388).
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