Mozilla could simply ship different packages for different countries, based on their patent laws. For example, US version could use binaries distributed by Cisco, while EU binaries could be built from source code maintained by Mozilla. IANAL but I think it would be completely legal as long as the company which distributes the EU version is a subsidiary or a separate legal entity located in EU.
You are free to use whichever package you wish. Of course it would be illegal if you live in a country that has software patent laws. But legality never stopped us from using VLC or Handbrake. Why should it now?