This thesis was circulated on social networks, in particular on telegram channels broadcasting pro-Kremlin rhetoric. Reports say that Ukraine is allegedly violating the Geneva Conventions by sending soldiers who have returned from captivity to the front lines. Like, the leadership of Ukraine is indifferent to the military, so they do everything as they want.
The specialists of the VoxCheck project investigated the case and determined that such a thesis is unfounded. In international humanitarian law, there is indeed an option of the exchange of prisoners, according to which a former prisoner of war is obliged not to return to military service. However, this is one of the options, so there is no evidence that Russia and Ukraine agreed on just such a release from captivity, because there are other formats for the exchange of prisoners.
There is no single rule in international law that all former prisoners of war must refuse to take part in hostilities. According to Jeroen van den Boogaard, researcher, consultant on international law in the Legal Department of the Ministry of Foreign Affairs of the Netherlands, international humanitarian law provides for 4 options for the release of prisoners of war before the end of hostilities:
conditional early release of prisoners fit for service. Typically, the dismissal comes in exchange for a commitment not to use arms again in the same conflict; however, the International Committee of the Red Cross (ICRC) claims that the practice of such dismissal has been significantly reduced since 1949, and many states today prohibit their military from agreeing to parole;
the release of captives fit for service who were held captive for a particularly long period; such an exchange could be arranged using intermediaries such as a neutral state or the ICRC;
the release of wounded or sick prisoners of war who will benefit from treatment in a neutral state;
the release of prisoners of war who, for health reasons, are unlikely to be able to continue to participate in hostilities.
It is not known for certain which of these options Russia and Ukraine chose. The Ukrainian bodies involved in the exchange of prisoners of war did not report that the dismissed fighters would not be able to return to duty again, and did not disclose all the details of negotiations with Russia. Former prisoners also cannot publicly talk about all the details. At the same time, there is confirmation that in Ukraine there is no ban on the return of former prisoners to military service.