The appointment of the applicable law to appeal against fraudulent acts of a bankrupt in cross-border insolvency proceedings is a complex process that is not uniformly accepted by law. The application of the statute of lex fori concursus in relation to the principles of nullity, appealing or relative ineffectiveness of legal acts performed against the general creditors does not raise any objections and is accepted due to the effectiveness and efficiency of the bankruptcy proceedings. Mechanism which is based on art. 16 of the Regulation 2015/848 provides the possibility of raising a charge of subordination of a given act to a law other than the law lex fori concursus, which allows the absolute subordination of this act to the law of the state of proceedings, despite the lex causae law. The appointment of the applicable law to the legal act has not been uniformly implemented so far. As a result of this, there were two views, one of which allowed the application of conflict‑of‑law rules in the lex fori concursus state, contrary to this view pointed the necessity to apply to the private law rules of private international law according to the country of the court of competent jurisdiction. Currently, matters related to appealing against bankruptcy are subject to the jurisdiction of the court with jurisdiction to initiate proceedings, which results in recognition that applicable law will be determined by the state’s conflict‑of‑law rules of instituting bankruptcy proceedings, which in turn serves predictability of the law and its effectiveness.