Despite the eagerness with which all EU governments embraced the idea of Europe-wide anti-terrorism measures, the Government is not expected to have its proposals ready before the middle of next month. This is because the area is a very difficult and complex one, raising questions of both constitutional and international law.
The problems the drafters face are considerable but, supporters of the measures believe, not insurmountable.
The first will be defining terrorism. While no one denies that the attacks on the US were terrorist attacks, the question becomes more difficult when people are fighting regimes where the majority of the population have no democratic outlet for their aspirations. Already a number of European states have exceptions to their extradition law allowing for political offences, and this is deeply embedded in European legal tradition.
One way around this would be to define terrorist acts, rather than terrorist movements. This could be done by introducing the legal principle of proportionality - the need for proportion between the act and the objective. Some actions would be likely to be defined as unjustifiable in any circumstances. The most obvious would be attacks on civilian targets. A precedent for this exists in international law with the anti-hijacking convention, making the hijacking of an aircraft a crime in any circumstances.
If a common definition of terrorist acts is arrived at, the next issue will be common measures to tackle them. The proposals on the table include a single European arrest warrant, involving the enhancement of the role two European bodies, Europol (the pan European police intelligence exchange network) and Eurojust (the prosecutorial co-operation network), and finalising a common approach to money-laundering and to asylum-seekers.
A common EU arrest warrant would effectively remove the courts from the extradition process. The Irish courts have been assiduous in examining extradition warrants, and there are likely to be concerns about this, especially if there are any doubts about the criminal justice system in the receiving state.
Having a common EU arrest warrant will involve Europol and Eurojust. The former, based in The Hague, shares intelligence between national police forces. Antonio Vitorino, European Commissioner for Justice and Home Affairs, has said Europol should have the right to initiate its own investigations. This could have implications for the autonomy of national police forces.
Eurojust, which so far only exists informally, will co-ordinate the EU states' prosecuting authorities, and is expected to get going officially at the end of the year.
But both these organisations will have to confront the divergence between the way most EU states conduct investigations, and the manner in which this is done in the common law countries, notably Ireland and the UK.
In most EU states investigations are carried out by magistrates, who prepare a dossier, and examine the evidence against the accused. People can be held in custody while the investigation is going on.
Here the police investigate, the prosecution prepares the evidence against the accused for the court, and this is tested in a totally independent court through the adversarial system. Once a person is arrested here, he or she must be charged and brought before a judge within a few days.
This is not just a theoretical problem. If a crime has international dimensions, and a person is arrested in one country for crimes committed in other countries, the investigating police officer may not know what court the person will end up before. This means he or she will not know what formalities need to be observed, what rights need to be guaranteed.
In the past there have been challenges in the Irish courts to evidence taken, for example, in Northern Ireland, which may not have been in accordance with our constitutional rules. We have also operated much stricter rules in relation to preserving chains of evidence than even the UK. If a person was arrested in another EU state and brought here for trial, he or she might not have had such rights respected, and the evidence would be open to legal challenge.
There will also be problems in relation to the evidence itself. In most of Europe it is dossier-based. But our justice system is based on oral evidence, and the right to cross-examine witnesses.
As the debate develops, there will be broader concerns. Will these measure conflict with our well-established constitutional protection for the rights of the accused?
If they are introduced as part of EU law, this will not arise, as they will be protected by the European treaties we signed, and the constitutional referendums permitting them.