I don't think it can actually, artbrooks, though I stand to be corrected.

But in any case this ban doesn't just apply to people who may have been involved in the incident - it appears that "there is a blanket U.S. policy of noncooperation with the civilian inquiries" (from that Washington POst story I linked to earlier.)

That evidently means no representatives of the US military at all, and no evidence supplied directly to the court - "The Times said the document states the U.S. will now only hand over their confidential findings to British military investigators and the British government must request U.S. approval before providing information to coroners' civilian inquests."

That's not exactly a friendly attitude.