Translate the following English sentence to French:
"In this case, we are dealing with the thorny issue of trying to ensure that vessels which are not part of the organisation respect the rules laid down by regional fisheries organisations. Such vessels, whether operating under flags of convenience or not, simply act freely whilst others respect provisions on the conservation of resources and, of course, contribute to these respective laws."
Il s' agit en l' occurrence de l' épineux problème du respect des règles des organisations régionales de pêche pour les navires non contractants, battant pavillon de complaisance ou non, qui exercent librement alors que d' autres observent les mesures de conservation des ressources et, bien évidemment, y contribuent financièrement.