Parent is right, sort of - it's only in US for now. It would be interesting to see this tested in other courts of law and included in trade agreements.
Judges in Europe have ruled that software licenses are contractual agreements. So we already have some case law in some countries establishing this.
The tricky bit in common-law countries like the USA and UK is that normally, a contract requires three things: an offer, acceptance, and consideration -- something of value exchanged for the offer in the contract. No consideration means no contract, and the license reverts to a bare license -- one that can be revoked at any time for any reason. If we now have case law establishing that the GPL fulfills the requirements of a contract, that will make software under the GPL safer, as it will not be at risk of having the copyright holders revoke permission to use or distribute it once it's out there under the GPL.
