By Dominic Casciani
It is a major decision about the legality of using secret evidence
The government says some terror suspects could come off control orders because of a ruling on secret evidence.
The Law Lords say the suspects must be given some idea of the evidence against them so they can defend themselves.
But Security minister Lord West told peers the judgement could may mean some of the orders would "have to go".
He said the Home Office would need to find an alternative measure to monitor the suspects - but not all the control orders were affected by the judgement.
In a major ruling last week, nine Law Lords unanimously found that it was unfair that individuals should be kept in ignorance of the case against them.
Their ruling, which some of the Lords made reluctantly, followed a precedent on secret evidence at the European Court of Human Rights.
The Lords did not quash the three control orders - but sent the cases back to the High Court for fresh hearings.
In practice, this means the Home Office has a choice between putting more intelligence material in the public domain or dropping cases if it does not want to reveal more information.
In the Home Office's first statement to Parliament on the ruling, security minister Lord West of Spithead said: "We have to have a way of handling some very dangerous people.
"We are going to have to go through each one on a case-by-case basis. These are highly complex issues."
He acknowledged that one of the Law Lords had warned that their ruling could spell the end of the orders - but that the alternatives to control orders appeared to be "hugely expensive" and lacking a similar level of monitoring of suspects.
"We will go and look at each one individually it's quite clear that not all the orders will be adversely affected by this judgement.
"As regards the other ones, if they don't pass the test, clearly we will follow what the direction is here and those control orders will have to go.
"And what we will have to do is put in place something to ensure the safety of this island because that's our greatest priority and that will be difficult."
Lord Lloyd of Berwick, a former Law Lord who reviewed terror legislation in the 1990s, told peers: "This is the second time on which a major piece of government anti-terrorism legislation has come unstuck.
The government should now phase out all existing control orders as soon as possible and come up with some other means of meeting the terrorist threat in a way that is consistent with the defendant's right to a fair trial.
"In particular the defendant must know, if he is to have a fair trial, the case that he has to meet."