Mere words are inadequate to describe the horror of Omagh. In the wake of such carnage it is natural and appropriate to examine our existing Offences Against the State legislation to see if it is adequate to meet the new security threat.

It is vital that any such legislation should meet two tests: first, will it work and, secondly, is it compatible with the Constitution and the principles of the rule of law and the fundamental tenets of criminal justice embodied therein?

It is my contention that changes to the Offences Against The State Acts alone will not provide a ready answer to the new security threat. It is true that the Oireachtas might usefully amend and improve aspects of this (and related) legislation - and in this the Tanaiste is quite correct when she points to the inadequate penalties which are sometimes imposed on persons found guilty of providing "safe" houses or even storing ammunition and explosives. But the basic point holds true - "ordinary changes" to anti-terrorism legislation will not in themselves bring peace, still less crush illegal organisations dedicated to the use of political violence.

This sorry fact is, regrettably, borne out by all the empirical evidence. If it were otherwise, how could the IRA have conducted a ruthless guerrilla campaign in the teeth of the draconian anti-terrorist legislation which exists both in this jurisdiction and in Northern Ireland?

Moreover, the Oireachtas twice legislated in the 1970s in response to the kidnap of Don Tidey. The government promised new legislation, but later the plans were quietly dropped, mainly, it seems, because it was concluded that no useful changes could be made to the present corpus of legislation.

Internment apart, two major proposals are presently under consideration. The first involves amendments to the Offences Against the State Act 1972, which permits the courts to receive the opinion evidence of a chief superintendent to the effect that the accused is a member of an illegal organisation. Although this provision was highly controversial at the time it was enacted, it was quickly neutralised by the courts.

In the Ferguson case (1975), the Court of Criminal Appeal held that the courts were not bound to act on such opinion evidence and indicated that they should not do so where this was the sole evidence and the accused had denied membership on oath.

It is hard to see how the Oireachtas could constitutionally circumvent this decision. Certainly, it could not validly oblige the courts to convict on the basis of this opinion evidence alone. There is already a large body of judicial decisions to this effect and it suffices for present purposes to point to the McEldowney case (1983), where the Supreme Court invalidated part of the Street and House to House Collections Act 1962. The significant fact here is that the provision which was found to be unconstitutional in that case had purported to direct the District Court to decide a case in a particular way once a senior Garda officer gave his opinion that the proceeds of any monies so collected were destined for an illegal organisation.

Any radical changes to the 1972 Act designed to make it easier to convict of membership charges based on Garda opinion evidence are thus likely to face formidable constitutional challenges. This is no mere constitutional technicality, as otherwise the courts would, in effect, be little more than sentencing tribunals. In reality, it would be a form of internment with the courts conscripted by the Oireachtas into performing the dirty business of the executive, by being obliged to convict on the basis of Garda opinion evidence alone.

If we were reduced to this, it would be a perversion of the Constitution and the legal system. In fact, internment would be a far more honest option, since it would be an open admission that the ordinary legal system cannot cope and it would avoid the (quite unconstitutional) sham of forcing (as opposed to the present system of entitling) the courts to convict on the basis of Garda opinion alone.

The second option is to move from the present 48-hour detention to seven-day detention for suspects. This suggestion has a number of practical difficulties. First, unless such detention was court ordered and supervised, seven-day detention would be unconstitutional.

If it were court ordered and supervised, it is likely that the judiciary would draw the teeth of any such measure by refusing to sanction seven-day detention, save in the clearest of cases. Alternatively, the Houses of the Oireachtas might declare a renewed state of emergency under Article 28.3.3 of the Constitution, thus giving constitutional immunity to any legislation allowing for unqualified seven-day detention.

This last happened in 1976 and the unhappy experience was also ineffective. The dangers of the courts acting on the basis of confessions obtained after very long periods of detention and interrogation are plain for all to behold.

And what serious evidence is there that the gardai have been seriously hampered by a 48-hour detention period? To sum up, therefore, by all means let the Oireachtas review the Offences Against the State Acts to see if they can be amended and improved.

But the key point is that draconian and far-reaching as this legislation is, it is nonetheless - with one exception - a court-orientated and court-based system of criminal law. Such a system cannot - at least using methods compatible with the Constitution and the rule of law - on its own crush a ruthless paramilitary organisation.

The one exception is the powers of internment contained in the Offences Against the State (Amendment) Act 1940. One must frankly state that such provisions are not compatible with the rule of law and the Act survives constitutional challenge thanks to a 1940 Supreme Court decision. The constitutionality of this Act almost certainly cannot now (for highly specific technical reasons) be re-challenged.

Despite this (majority) war-time Supreme Court decision, this measure ought really to have been found to have been unconstitutional, since it is an extra-constitutional measure appropriate only to emergency legislation specially enacted under cover of Article 28.3.3.

Internment is clearly a measure of last resort which any democracy must be exceptionally loath to use. There are a thousand reasons against its use as it might backfire and quickly become politically unacceptable. But at least it has a measure of honesty - it is a frank admission that ordinary legal measures and the ordinary legal system cannot cope, such are the dimensions of the paramilitary threat.

Despite the horrors of Omagh, we can only hope that measures of last resort will not have to be used. But if we as a community are forced to choose between two quite unpalatable measures, for my part I would prefer the open honesty of selective internment - if accompanied by the humane detention in civilised conditions of leading suspects - to further attempts to undermine the fundamental principles of our criminal justice system, with the attendant risks of police brutality, forced confessions, miscarriages of justice, unacceptably long detention periods, abolition of the right to silence, the perversion of the rules of evidence and, ultimately, the discrediting of the legal system itself.

With the law - as with life itself - honesty is the best policy.

Gerard Hogan is a lecturer in law at Trinity College, Dublin, and is the co-author (with Prof Clive Walker) of Political Violence And The Law In Ireland.