To use the justice system most effectively to stop leaks you have to make two decisions.

First, you have to decide what will be a basis for punishment. In the case of a leak you have essentially two signals you could use. You know that classified documents are circulating in public, and you know which parties are publishing the classified documents. The distinctive feature of the crime of leaking is that once the documents have been leaked you already know exactly who will be publishing them: The New York Times and Wikileaks. Regardless of who was the original leaker and how they pulled it off.

That is, the signal that these entities are publishing classified documents is no more informative about the details of the crime than the more basic fact that the documents have been leaked. It provides no additional incentive benefit to use a redundant signal as a basis for punishment.

Next you have to decide who to punish. Part of what matters here is how sensitive that signal is to given actor’s efforts. Now the willingness of Wikileaks and The New York Times to republish sensitive documents certainly provides a motive to leakers and makes leaks more likely. But what also matters is the incentive-bang for your punishment-buck and to deter all possible outlets from mirroring leaks would be extremely costly. (Notwithstanding Joe Lieberman.)

A far more effective strategy is to load incentives on the single agent whose efforts have the largest effect on whether or not a leak occurs: the guy who was supposed to keep them protected in the first place. Because when a leak occurs, in addition to telling you that some unknown and costly to track person spent too much effort trying to steal documents, it tells you that your agent in charge of keeping them secret didn’t spend enough effort doing the job you hired him to do.

You should reserve 100% of your scarce punishment resources where they will do the most good, incentivizing him (or her.)

(Based on a conversation with Sandeep.)

Update: The Australian Government seems to agree. (cossack click:  Sandeep)