Guest blogger Joan Kelly writes:
As followers of the saga of the Boston College subpoena will be aware, the text of the demand for access to the oral history archive has been sealed, which means that relevant details – the who is behind this and why they are doing it for instance – have been hidden from the college and therefore the general public. But the secrecy doesn’t end there. In this remarkable piece written by Chris Bray of the History News Network, you can see that the US Department of Justice, which is facilitating the subpoena request on behalf of the British government, is refusing to answer even the most basic questions about the matter, not even which treaty between the US & UK is being used to authorise this request. Why such secrecy? What is going on here?
The Broken Elbow 
I believe the Treaty permitting the subpoena is the 1994 Treaty Between the Government of the United States of America and the Government of the United Kingdom of Great Britain and Northern Ireland on Mutual Legal Assistance in Criminal Matters. There is also a statute here in the United States, 28 USC 1782, Assistance to Foreign and International tribunals which comes into play.
The fact that there is no actual pending case in Northern Ireland appears not to matter, according to the case law, which has found that it is suficient if judicial proceedings are within reasonable contemplation.