The announcement by British Attorney General Lord Goldsmith that American military tribunals will not offer "sufficient guarantees of a fair trial" is the culmination of a long process of negotiation, not a sudden decision by Britain to distance itself from the United States.
In fact, Foreign Secretary Jack Straw said much the same thing back in February of this year.
The US Supreme Court is due to decide whether it should intervene
"Some progress" had been made, he said, but the military tribunals or commissions "as presently constituted would not provide the type of process which we would afford British nationals."
So this has always been a problem between London and Washington.
However, that said, it is quite useful both domestically and internationally for the British government to be making a stand on this issue.
It provides at least one major subject which distinguishes British from American policy in the "war on terror" declared by President Bush after the attacks of 9/11.
It is also in line with a new emphasis Mr Straw himself is putting on international law.
In that context, the criticism is significant as it implies that the United States is not following the principles of international law closely enough.
In an article Mr Straw co-wrote with the Swedish foreign minister, Laila Freivalds, recently he said: "Global threats such as terrorism pose new challenges for international law.
"The universal adherence to and implementation of the 12 UN Conventions against terrorism is a priority.
"It is also imperative, for political, legal and moral reasons, that human rights and international humanitarian law are respected in the fight against terrorism."
The military tribunals or commissions in question will be run by a panel of US officers.
The presiding officer can admit any evidence he or she considers that, in the words of the Presidential Military Order, a "reasonable person" would consider relevant. Defence lawyers will also be from the American military.
A conviction can be made by a majority vote. There will be a military review panel for any appeal though a final decision can go to the US Defence Secretary or even the President.
In negotiations with the US authorities, Lord Goldsmith won some concessions. He was promised that the two Britons named as facing tribunals would not be given the death penalty.
They could hire British lawyers as "consultants." Their legal discussions would not be monitored and they might be able to serve any term of imprisonment in Britain.
Lord Goldsmith feels that these concessions do not go far enough. His main concern is the appeals procedure.
He feels that appeals should go to a civilian court, not to a military review board.
Another British concern is the admissibility of almost any evidence at the discretion of the tribunal including hearsay and evidence perhaps produced by torture.
Lord Goldsmith has won some concessions
His position is supported by Major Michael Mori, one of the American officers appointed to defend one of the suspects, the Australian David Hicks.
Major Mori is one of those characters who stands up against the system which produced him.
In comments in London in March he said: ""The system is not set up to provide even the appearance of a fair trial. If there's credible evidence, take him to an established justice system. If it's not credible, that doesn't justify changing the rules.
"When you use an unfair system, all you do is risk convicting the innocent and providing somebody who is truly guilty with a valid complaint to attack his conviction. It doesn't help anyone."
Australia says yes
In contrast to the British position, the Australian government has accepted the amended rules, including a right by the Australian government to make a submission to the review panel.
An announcement was made in November last year that "the United States and Australian governments agree the military commission process provided for a full and fair trial."
The phrase "full and fair trial" is taken from the Presidential Order and is the principle which the Order says governs the whole procedure.
In the meantime, the whole issue is likely to have to wait until the US Supreme Court decides whether it should intervene over the Guantanamo prisoners. A ruling is expected soon.