Well, a few thoughts.....
International Lawsuits for Copyright Infringement Do Exist
There have been quite a few international copyright actions. Perhaps the most pertinent is Kazaa. They started out in Holland, and were purchased by a company that operated out of Australia and were incorporated in Vanuatu. They were sued in American courts, and ultimately settled. My knowledge is incomplete, but I do not believe jurisdiction prevented any of the lawsuits from proceeding.
Allofmp3.com, whose servers were in Russia, was also sued in American courts. Unlike Kazaa, they were not operating a p2p network, their servers were all in Russia. They did try to claim the American courts did not have jurisdiction, but shut down before the case was decided.
As mentioned earlier, there's also the "Stormtrooper Costume" case currently under way in the UK, so we'll see how that turns out.
Again, this is an extremely complicated field of law, so I cannot categorically state "yes PGA can be sued." However, the fact that no one has done more than send a warning letter to PGA is not proof either way.
Passivity Does Not Excuse Responsibility
This is a bit more clear in the law. Namely, most P2P networks and services can legitimately be viewed as passive agents in any infringing file sharing. Napster, Kazaa, Grokster and the Pirate Bay are not actively uploading and hosting infringing content; they are operating open networks, which let the users share whatever content they so desire.
The courts have upheld that this does not absolve them of legal responsibility in multiple jurisdictions, including the US, Australia and Sweden.
Similarly, Youtube is in a dispute with Viacom. So far the courts have held that Youtube may not be required to actively hunt down infringing content on its site, but is still responsible if they are notified of an infringing video. Youtube has fully accepted that responsibility.
None of this guarantees that GPA would lose a case, only that there are a few examples where passivity does not absolve responsibility -- especially once you are notified.
Morally Unpleasant Examples
Just remember, I was not the one who introduced extreme moral examples...
Let's say that the nation of Greater Berzerkistan legalizes the production and distribution of child pornography, and does not bar sharing or exporting such goods outside of Berzerkistan's borders. Trff Bmzklfrpz sets up a studio and a server, and happily provides his content to anyone outside his nation with a Paypal account, along with a disclaimer stating that he cannot vouch for the legality of the content.
• Can Trff be arrested?
• If not, should Trff voluntarily restrict his content to Berzerkistan anyway?
• Is Trff morally responsible for his actions, even if he believes he is engaged in a legitimate activity?
Or: A woman in an almost-empty restaurant starts choking on a bit of food. I sit by passively and let her choke. There is almost no risk to my health and safety if I assist her, yet I do nothing. Am I in the clear, legally and morally, if she chokes to death? Does my passivity absolve any possible responsibilities on my part?
My position, by the way, is that sharing materials that are PD in one nation, and not in another, is a fairly trivial moral issue. Even if they intend to violate US copyright durations and know/believe that the disclaimer is a joke, it's still pretty trivial. This is why I've tried to avoid examples
in extremis, because I for one think the stakes can change when the conduct under discussion has more significant consequences.
I don't think PGA's servers should be seized by the AFP, or block any visitor from outside of Australia, or that they should pull the content completely. I just think that if they're going to rely upon a respect for the expiration of copyright laws that makes it 100% legit for them to distribute PD materials, they should make a good faith effort -- especially when they receive a specific request -- to block content from the locations where it is not PD. The disclaimers, in my opinion, fail that particular test; an IP block, which still would hardly guarantee accuracy and will not block a determined infringer, is just a better demonstration of respect for IP terms abroad.
Moreover, PGA is not standing up to defy an immoral law. They're basically just calling a lawyer's bluff. It's not quite the same thing, in my opinion.
Geo Restrictions
I guess I misread your post -- I assumed you were recommending some type of legal changes to remedy the situation.
I agree the contracts can, and probably will, be revised. My feeling though is that the economic incentives will do most of the real heavy lifting. If/when a country gets close to the "ebooks are 10% of the market," I think you'll see a LOT of big changes and a lot more international availability.
That said, there actually are reasons why some things won't change, mostly due to cultural issues. If I was an American author working with an American publisher, there is no way I'd trust them to really do a good job selling my book to a French audience, let alone translate it well.
Signing on with a French publisher will almost certainly produce better results and stronger local incentives.
For small sales, possibly up to midlist authors, this probably isn't relevant, so those authors will likely just throw open the gates.
But I do expect the general system to continue, especially for authors who really want to make a go at international sales.