In the 1930s, the Supreme Court deemed prior restraint unconstitutional, except in cases of national security issues. This issue was dormant until the planned publication of the Pentagon papers by the New York Times and the Washington Post. The Nixon Administration tried to use the national security exception to issue an injunction against the publishing of these documents, but a fragmented Supreme Court struck down the injunctions (though they did issue nine separate opinions in doing so).
I asked Mr. Fleischaker what he thinks would happen if the WikiLeaks situation was put in place of the Pentagon Papers--that is, what would happen if the United States tried to issue an injunction barring WikiLeaks from releasing any more cables (putting aside the logistical issues that would be involved in such an attempt). Fleischaker stated that he thought the Court would issue the same ruling, that the national security exception would not apply. He went on to say that the Supreme Court did not say that the Nixon Administration couldn't try to punish the New York Times or Washington Post if and when they published the Pentagon Papers, just that the government couldn't prohibit the publishing in the first place.
That, as the kids say, ain't enough. If the national security exception does not apply in this case, then where exactly would it apply? Fleischaker's argument is that allowing the government and judges to determine what is and what isn't important to national security is the beginning of a slippery slope to increased censorship. At first glance, I think this argument is a solid one, but if the leaked information is classified, that mean the government has indeed declared the information to be secret. I don't think anyone is decrying the system of classifying information as illegal, and if that's the case then it should be legal for the government to pursue legal measures such as prior restraint to keep the information secret.
Leaving an option to punish publishers after information is released is akin to closing the barn door after the horses have gotten out. The U.S. government should be legally allowed to go after organizations like WikiLeaks before the information is released in order to minimize potential national security damage.