Tuesday’s instalment of what has become a “theatre of blood” from Iraq and Syria will horrify and revolt all right-thinking people. That some of the perpetrators of these acts are British nationals born and brought up here increases the sense of outrage and the concern that such individuals may seek to behave in the same way if they return.

As one of the principal responsibilities of the government is to safeguard its citizens, it is entirely reasonable that it should look at what more might be done to improve security. In making his statement on Monday the prime minister was fulfilling that duty.

But, as was clear from the statement, the armoury of the criminal justice system is pretty full. Whether it be the Foreign Enlistment Act 1870 or the Terrorism Act 2000, there is no shortage of offences with which to prosecute those who go abroad to fight or train and who may threaten us on their return. The number of cases this year suggests that MI5, the police and the CPS are being successful in bringing them to justice where evidence is available.

As has been the case throughout the history of terrorism, government anxiety centres on what to do about those against whom there may be intelligence but no usable evidence. The public are perceived as unlikely to be tolerant of those in authority who see a risk but do nothing about it. But departing from ordinary principles of justice brings its own problems.

The proposals announced on Monday illustrate this. Better passenger information from airlines may not be a major issue. Allowing police to confiscate passports at the UK border to prevent an aspiring young jihadi from leaving for Syria via Istanbul may be justifiable on good intelligence and a sensible extension of the home secretary’s powers. But unless there is some rapid means of review there must be the likelihood that mistakes will occur as the use of this administrative power increases and perfectly innocent young people will find their travel plans wrecked.

We would be wise to insist on oversight, rapid review processes and compensation where justified.

Nor should we blindly share Labour’s enthusiasm for control orders. They worked far less well than was trumpeted when they were introduced. We were right to replace them with less restrictive measures and I welcome the fact that the changes proposed do not constitute a complete return to them. I am confident, however, that David Anderson QC, the independent reviewer, would not advocate greater powers without good reason and that what I saw of the problem in government can justify such a measure provided the existing rights of challenge and review are maintained.

But as I explained in parliament, I find it difficult to see how a proposal to prevent a British national from returning to our country could be carried out, even temporarily, without legal, practical and reputational problems for us. The prime minister rightly emphasised that we must not breach international law by rendering a person stateless. But what is refusing to allow a person back with no other nationality, but an assertion of just such statelessness? How would my friend and colleague the home secretary have felt if, at the last minute, the Jordanian government had done the same to us over Abu Qatada? Where are the common law principles of freedom under the law and the presumption of innocence if individuals cannot return to face prosecution and trial in their own country on grave allegations that are being levelled at them? How would a temporary ban assist security, except temporarily?

While I am open to argument to the contrary, I would be surprised if further work does not reinforce these difficulties. The prime minister was wise not to be lured by the odder suggestions that have been floated of banning some foreign travel altogether or reversing the burden of proof in establishing innocent motives for travel where such travel has occurred without official permission.

The hard truth is that there is no easy solution to the problem of young jihadis and none of these proposals will on their own give us security. That will only come from winning the values battle that confronts pluralist democracy facing violent fantasists obsessed with the creation of “ideal” societies that reflect their views.

Believing in and practising the principles of the rule of law is, with our liberty and democracy, among the most powerful weapons we have. It is less effective if we blur its clarity and we should do this as sparingly as possible.