The three men convicted in the United Kingdom on Monday of a plot to bomb several transcontinental flights were prosecuted in part using crucial e-mail correspondences intercepted by the U.S. National Security Agency, according to Britain’s Channel 4.

Although British prosecutors were eager to use the e-mails in their second trial against the three plotters, British courts prohibit the use of evidence obtained through interception. So last January, a U.S. court issued warrants directly to Yahoo to hand over the same correspondence.

It’s unclear if the NSA intercepted the messages as they passed through internet nodes based in the U.S. or intercepted them overseas. If the former, it’s possible the interception was part of the Bush administration’s warrantless surveillance program — a surveillance program aimed at intercepting foreign correspondence as it passed through domestic internet switches.

Its possible that these emails were obtained illegally, which is an interesting datapoint for the TSP. There is quite an argument in the attached thread.

Basically, Yahoo is a US entity. Intercepting communications between Pakistan and Yahoo involves a US party, even if the content of that communication is an email that someone in the UK is going to pick up from Yahoo later. Traditionally, a FISA warrant would be required for that. Under the TSP the NSA was picking this stuff up without a warrant. The change to FISA made in the last days of the Bush administration was intended to allow them to do that going forward.