The principle of relativity, as originally expressed by Galileo, points out that the area of competence of the principle itself is that of isolated systems as well as inertial reference frames. The principle does not claim that it is always possible to isolate any physical system; indeed it leaves it open to the possibility of the existence of phenomena concerning nonisolable physical systems, e.g., phenomena regulated by some nondraggable ether. After the Aspect experiment realist and local models have been proposed specifically based on the hypothesis that entangled systems are not isolated. It is hypothesized that the correlations which allow the violation of Bell's inequality are due to exchanges of superluminal signals between the various parts of the system, and those signals do not generate causal paradoxes because their propagation is regulated by a nondraggable ether. In the present paper the perfect compatibility of such models with the relativity theory is strongly advocated. A criterion is finally proposed to determine the causal ordering between events since, when there are superluminal signals, that ordering can no longer be associated to the time ordering induced by the standard synchronization.