In a file photo taken on January 20, 2009, British hacker Gary McKinnon leaves the High Court in central London. (Photo: AFP)

On Tuesday, British Home Secretary Theresa May announced in the House of Commons that Gary McKinnon, who has acknowledged hacking into U.S. government computers, would not be extradited to the U.S. because he was mentally ill, and extradition would therefore violate his human rights.

The U.S. Department of Justice responded that it was “disappointed” with this decision but stressed the strength of the U.S. extradition relationship with Britain. The Washington Post described Britain as seeking to “roll back” the U.S.–U.K. extradition treaty.

This treaty, signed in 2003, is the subject of much popular and press mythology, and the McKinnon case has been the subject of an enormous public campaign in Britain. His supporters claim that, as his mother puts it, he was “a classic computer nerd. He was looking for UFOs.” But in a 2005 interview, McKinnon acknowledged a somewhat different set of motives: He hacked U.S. government computers “to screw the Americans,” to find information about extraterrestrials that would prove the U.S. had suppressed information about the existence of anti-gravity technology that would provide free energy for the world, and to answer “hundreds of unanswered questions about 9/11.” This interview provides some justification for believing that Home Secretary May has accurately assessed McKinnon’s mental condition.

But in any event, U.S. commentators have ignored a basic point. May’s decision does not prove that the treaty has failed. It proves that the treaty works. Under the 2003 Extradition Act, May had the authority, fully compatible with the treaty, to decide not to extradite McKinnon. The U.S. made a lawful extradition request for McKinnon, and Britain considered it in a lawful way and decided, based on what appears to be creditable evidence, not to proceed. The subject is therefore closed. Moreover, as May pointed out, this case was “difficult and exceptional,” the U.S.–U.K. treaty is “broadly sound and…brings benefits to both our countries,” and the major change demanded by the treaty’s critics—the introduction of a prima facie evidence test—is unnecessary.

The changes that May did announce are significant, and many of them are good. British prosecutors will receive new guidance in cases of concurrent—that is, U.S. and British—jurisdiction, a relevant bilateral protocol between the U.S. and Britain is being updated, and in future, the High Court (not the Home Secretary) will be responsible for assessing human rights considerations. These are all sensible measures; the involvement of the High Court, in particular, might reduce the ability of future McKinnons to conduct high-profile public campaigns.

May’s announcement that Britain will implement a “forum bar” is potentially problematic. A forum bar gives a British court the power to bar prosecution overseas if prosecution is possible in both Britain and another nation (such as the U.S.). This is compatible with the treaty, which already gives Britain (in the case of U.S. requests) the right of first refusal on prosecutions. What is troubling about the forum bar is that it adds another step to an already lengthy process, it reduces the scope for prosecutorial judgment on which both the U.S. and Britain rely, and—for some—it is intended to create “a presumption in favor of British trials for British citizens.”

That sounds reasonable, but it would imply that only British subjects, not foreigners, should be shielded from foreign trials. In short, it implies discrimination against foreigners, not the equal treatment under law that now prevails—and has long prevailed—in Britain. That would be a genuinely new and undesirable step. But it is too soon to do more than express concern about this: The impact of a forum bar cannot be assessed until the necessary legislation is introduced. And it may very well be that those who demand a forum bar will be disappointed by its results and that British courts will generally support the decisions of British prosecutors that particular cases should be tried abroad. It is all too easy to assume that setting up a new legal process will always get you the results you want, but that is not how genuine legal systems work.

For now, the most that can be said is that many of the changes announced by May are sensible, the McKinnon decision was completely legal, and that any extradition system conducted through legal processes will on occasion produce results that some do not like. But as May rightly recognized, that does not mean that the system needs to be rolled back.