This is the latest in a series of cases where the highest court in the UK (then the House of Lords Judicial Committee - which has subsequently become the UK Supreme Court) has ruled against Government attempts to restrict the activities of suspected but not convicted terrorists. The Court held that an individual in government control “must be given sufficient information about the allegations against him to enable him to give effective instructions in relation to those allegations. . . . Where, however, the open material consists purely of general assertions and the case against the controlee [individual held pursuant to a control order] is based solely or to a decisive degree on closed materials the requirements of a fair trial will not be satisfied, however cogent the case based on the closed materials may be.”
The full judgement can be read here