Patent law thus restricts the sovereign rights of States to exploit their genetic resources. In order to counteract increasing utilisation restrictions that are to the detriment of the countries of origin, the CBD, as well as various national legal systems, now acknowledge that the granting of patents must be subject to prior informed consent of the country of origin of the respective resource. However, the non-observance of this formal requirement does not invalidate the granting of a patent; it merely acts as an appeal mechanism. In this regard, export restrictions, aimed at the circumvention of the agreed ABS systems, seem to be a more effective method to strengthen the position of the countries of origin: if a patent is granted on an unauthorisedly exported genetic resource, the illegitimate patent can be challenged under certain conditions, e.g. by filing a patent revocation action..