We have of course only the US Government's word on that, as the foreign country which actually wanted the information checked the no-publicity box, and the US Government would like to keep it that way.
The implications of the rest of the Government's arguments are however more interesting than the use of the T-word as an all-purpose cloaking device, which is no more than par for the course these days. Primarily, the Government argues that the parties asking for the court order to be unsealed have no standing to ask this. The parties are the EFF, Urbana-Champaign Independent Media Center Foundation (an Indymedia grouping) and Jeff Moe. The servers were of course Indymedia servers, so UCIMC could be thought of as, or acting for, the proprietor of the sites hosted by Rackspace, while Moe is the owner and operator of the specific servers that were taken from Rackspace's premises in London.
The Government covers this as follows: "None of the movants have standing to file the Motion to Unseal." The subpoena, it says, was served on Rackspace in San Antonio, "the parties to the instant action are the requesting foreign country, hereinafter 'requesting state', the United States government and the party on whom the subpoena was served, Rackspace. The entities and one individual requesting the illegal unsealing are not parties and lack standing to complain of the alleged seizure."
The vast majority of web site 'owners' (inverted commas introduced courtesy US Gov) should have no trouble at all figuring out where they would stand in such a scenario. You operate a web site which is hosted by an external company, and an unidentified agency of an unidentified government has the power to take data which you own, but which is situated on hardware hosted by the external company, and according to the US Government, it's nothing to do with you, only the external company has the standing to complain. One could speculate why, given the need to maintain some form of ongiong relationship with the FBI, a hosting company might not think it a particularly good idea to complain.
In the specific circumstances of Indymedia, a process that was started in Texas resulted in the removal of servers in London, knocking out numerous Indymedia web sites. According to the US, Inydmedia has no standing to complain about this or to seek redress, or to find out what it was supposed to have been doing, or who said it was doing it. The UK Government insists the whole matter is nothing to do with it, while the US Government says the matter is closed, flashing the T-word to be on the safe side.
The level of "redress" put forward by the Government as apparently adequate should also concentrate minds. "Movants state Moe received no justification nor any avenue for redress," it says: "Neither are true. Moe was told by Rackspace they received an order and were bound to comply with it. Movant Moe was offered his servers back but refused. Subsequently he demanded and was given new servers by Rackspace. As Movants have no standing their request to unseal should be denied."
So if your business is paralysed by the removal of all of your data by governments unknown, being given it all back a week later is perfectly fine as far as redress goes. Note that under the Mutual Legal Assistance Treaty (MLAT) used it's likely that the US Government only needs to hand seized evidence back if and when it is possible. It is therefore perfectly conceivable that all of your business could have been seized and gone somewhere, it could stay there forever, and you still wouldn't have any standing to complain about it. The Government's argument here, as far as we can gather, is in any event a seriously twisted interpretation of what happened. When the servers were returned Moe declined to put them back online until they'd been thoroughly checked over, which would seem the sensible approach, and it would also seem sensible to go back online with newly-configured servers whose integrity you could be sure of. Moe's ingratitude here would therefore seem to amount to being sensible and professional.
The Government document confirms that the requesting state has asked under the MLAT "that the application for assistance, the contents of the request and its supporting documents, and the granting of such assistance be kept confidential." It then, non-ironically, quotes article 6 of the US Constitution.
The nature of the "ongoing criminal terrorism investigation" is of course classified, and we should trust them and the shy foreign government to be doing The Right Thing. The nearest thing to such an investigation that has been unearthed so far has been the admission by Bologna prosecutor Marina Plazzi that she asked for IP address information through an MLAT request, but did not ask for the server seizures. This could produce a plausible 'cockup' scenario where a request for a specific piece of evidence dominoed into the seizure, but such a seizure's disproportionality would not have been legally permissible under US or UK law or under either the UK-US or US-Italy MLAT. It is, theoretically, not possible to just grab everything and then trawl it, but on the other hand it's not - according to the US Government - allowed to either establish that such a thing happened or too get anything done about it, if it did.
In any event even the IP address request seems dubious. Plazzi is conducting an investigation into a fringe anarchist group in connection with bombings in Italy. Indymedia itself denies that such a group has ever posted to Indymedia sites, but even if you didn't believe that, it is desperately implausible that dangerous terrorists would expose themselves by conducting conversations on open web sites, never mind ones which are known as essential reading for the Italian security forces. But if a judge in any country in the world purports to believe this sort of tosh, then whole web operations can be destroyed, and there's nothing anybody can do about it. That is the US Government's case.