Alrighty then:
The Guardian has struck a partnership with the New York Times which will give the US paper access to some of the sensitive cache of documents leaked by the National Security Agency whistleblower Edward Snowden. […]
It is intended that the collaboration with the New York Times will allow the Guardian to continue exposing mass surveillance by putting the Snowden documents on GCHQ beyond government reach. Snowden is aware of the arrangement.
The premise of this is mostly legalistic, since in a world of flash drives and internets it is all but impossible for even a government to fetch back all copies of a given piece of data; giving the documents to an American outlet should in theory protect at least
that copy of the documents via American laws protecting American journalists. Presuming those particular American laws protecting journalists still mean what we think they mean, anyway—we've had a bit of a bad stretch ourselves, on that point.