I'm not a lawyer or a legal scholar either, but my older daughter just graduated from a Japanese law school, which I guess entitles me to have an opinion on this matter. (Not that any lack of entitlement ever stopped me from opining, but.) So here goes.

The government apparently thinks that TEPCO is liable (http://www.yomiuri.co.jp/politics/news/20110323-OYT1T00002.htm?from=tw). Here's a lawyer making the same point employing somewhat unlawyerly logic (http://www.yomiuri.co.jp/feature/20110316-866921/news/20110325-OYT1T00980.htm). This Twitter compilation
(http://togetter.com/li/114804 this and all other links in Japanese, sorry) illustrates how high the "grave natural disaster" hurdle is. This is why there is open talk about nationalizing TEPCO--shades of the financial crisis--to provide the legal means to fulfill all claims against TEPCO. The idea appears to be that the government will then keep TEPCO alive a la Chisso to recover its money. That means that the shareholders will take the first hit, then the customers will pay over the long-run.

Or will they?

This seismologist's interview
(http://www.jiji.com/jc/c?g=eco_30&k=2011032700097)
shows that the government, through its Nuclear Safety Commission, had an opportunity to adopt regulatory guidelines that might have prevented the massive failure--no doubt at significant cost to TEPCO. The 9.0 East Japan earthquake is exponentially larger in terms of the energy released than the 7.9 Kanto Earthquake. Moreover, the possibility of an earthquake of that nature--which being the cause of its extraordinary magnitude--at that site appears to have been ruled out by seismologists. (And you think weathermen catch a lot of flak...)

Does TEPCO have a case? I have no idea. All I can say is that its management wouldn't want to sue the government on my say-so, because Berlusconi is not going to try to bail them out when they face the wrath of the Japanese government and public, and much if not most of the media as the result. But shareholders may threaten to bring a lawsuit against them on behalf of the company if they don't. It could be argued that fund managers will have the fiduciary duty to do so on behalf of their investors. Now Japanese fund managers will not want to step into this cow pie and I'm not naming names, but there must be enterprising hedge fund managers overseas who must be looking into this angle right now.
Say, your friends, S------ G-----?