In an interesting article, Till Jäger explains how gpl-violations.org enforced the GNU GPL in European countries, as well as countries outside Europe, like Taiwan, Korea, the US and China. Till's conlusion:
The well-established practice of GPL enforcement in Germany and some parts of Europe leads to a growing number of GPL compliant products. Since embedded systems often contain third party software, enforcement cannot stop with legal actions against manufacturers or importers of infringing products, but must aim for compliance of the complete distribution chain and needs to have a more general strategy of information policy for such software developing companies and countries. Plenty of documentation exists that can be used for providing the software industries all over the world with the necessary know-how to avoid GPL violations. Considering the increasing use of GPL software in the software market, license enforcement will continue being an essential issue in the OSS world.
I highly recommend this article if you are interested to learn more about GNU GPL enforcement.