The Supreme Court rejected most of the grounds of appeal advanced by the Haugheys, including claims that the tribunal's discovery orders had violated their right to privacy and Mr Haughey's right to equal treatment.
It agreed with the High Court view that it was "bordering on the absurd" to suggest that Mr Haughey was being unfairly or unconstitutionally discriminated against as compared with other former Taoisigh, ministers or Ansbacher account-holders.
The court rejected the claim that the tribunal had acted in breach of constitutional rights and fair procedures in sitting in private at the preliminary investigative stage of its proceedings.
The court said it was satisfied the tribunal was entitled to conduct its preliminary investigation in private for the purpose of ascertaining what evidence was relevant and to enable it in due course to serve copies of such evidence on the appellants which it was obliged to do.
On a claim that the discovery orders relating to the bank accounts infringed the Haugheys' constitutional right to privacy, the court said it was satisfied they did not unjustifiably encroach on that right. It found the encroachment on such rights "is justified in this particular case by the exigencies of the common good".
The court also rejected a claim that a tribunal appointed by the Taoiseach could not exercise the powers conferred on tribunals of inquiry under the 1921 Act.
It was argued that when the 1921 Act was enacted, a tribunal could be vested with the powers under that Act only where it was appointed by the Crown acting on the advice of the Government or a Secretary of State. The court found that the powers under the 1921 Act were exercisable by the Government or any minister, including the Taoiseach.
Turning to another ground, the Chief Justice dismissed the claim that the resolution passed by Seanad Eireann regarding the Moriarty tribunal and identifying the matters to be inquired into was invalid because the Seanad had not been properly convened in accordance with the provisions of the Constitution.
The court said the underlying policy of the 1921 Act was not in doubt. It was to provide the machinery, wholly independent of the political process, whereby matters of grave public concern may be investigated and the true facts brought to light.
It found to be "unsustainable" the claim by the Haugheys that the establishment of the inquiry in the present case was in excess of the powers of the 1921 Act because it was not in aid of the legislative process.
It said it was not part of the function of the High Court or the Supreme Court to review a decision by the Oireachtas to establish an inquiry under the 1921 Act into matters "which are properly described as of `urgent public importance'."
The court also found unsustainable the claim that the Oireachtas should have availed of other forms of inquiry, such as a select committee of one or both Houses.
On the claim that the terms of the resolutions regarding the Moriarty tribunal were in excess of the powers of both Houses of the Oireachtas through being "arbitrary, vague and oppressive" and not identifying a matter of urgent public importance, the court noted the High Court had expressed a view on how the tribunal's terms of reference should be interpreted.
The Supreme Court was satisfied it was not the function of the High or Supreme courts to interpret the terms of reference at this stage. The interpretation was for the tribunal itself.
It noted the report of the Royal Commission of Tribunals of Inquiry 1966 in the UK (the Salmon Report) said a tribunal "should take an early opportunity of explaining in public its interpretation of its terms of reference and the extent to which the inquiry is likely to be pursued".
That report also stated: "As the inquiry proceeds, it may be necessary for the tribunal to explain any further interpretation it may have placed on the terms of reference in the light of the facts that have emerged."
The Supreme Court said it adopted those words as a correct statement of the law and practice applicable to such tribunals in Ireland. Accordingly, it did not find it necessary to decide whether the terms of reference were properly characterised as "vague".
It was for the tribunal to determine if the terms were capable of more than one interpretation, which was the preferred interpretation.
It said the Oireachtas resolutions regarding the establishment of the Moriarty tribunal clearly indicated the matters which the Houses considered to be of urgent public importance - the findings of the McCracken report on payments to politicians and regarding the Ansbacher accounts and the serious public concern arising from those findings.
The court said it could not be suggested that the matters referred to were not of urgent public importance or that it was not within the jurisdiction of both Houses of the Oireachtas to regard them as so or of the Taoiseach to appoint a tribunal "whose principal function was to restore public confidence in our democratic institutions by having the most rigorous public inquiry, consistent with rights of the citizens concerned, into the circumstances which have given rise to the public disquiet in the public case".
It found that in passing such resolutions, the Oireachtas could not be said to be acting arbitrarily or in abuse of power. It added: "Having regard to the circumstances outlined in the report of the Dunnes payments tribunal and the effect thereof as outlined in the recitals to the resolution, the court is satisfied that the terms of the resolution were neither arbitrary nor oppressive."
On the Haugheys' submission that the terms of the resolutions and the inquiries directed as a result of these violated the Haugheys' constitutional right to privacy, the court said there was no doubt the tribunal exposed the Haugheys and other citizens to the risk of having aspects of their private lives uncovered which would otherwise remain private and to the risk of having baseless allegations made against them.
What was in dispute was the extent of the right to privacy in particular where it extended to the right to confidentiality in respect of banking transactions and whether the exigencies of the common good outweigh, in the circumstances of the case, such right to privacy.
The court accepted the constitutional right to privacy, in the present case, ex tended to the privacy and confidentiality of a citizen's banking records and transactions, but it also said the exigencies of the common good may outweigh the constitutional right to privacy.
In the present case, the Oireachtas deemed it expedient there be an inquiry into matters of urgent public importance and passed resolutions to that effect. The effect of such resolutions encroached on the rights of the Haugheys but that encroachment was justified by the exigencies of the common good. Such encroachment must be only to the extent necessary for the proper conduct of the inquiry, it said.
The Oireachtas was entitled to assume the tribunal would conduct its investigation in accordance with the principles of constitutional justice and fair procedures and would only interfere with the constitutional rights of the Haugheys when, and only to the extent that, it was necessary for the proper conduct of the inquiry. That ground must also fail.
The court went on to reject the argument by Mr Haughey that the Oireachtas resolutions discriminated against him and violated his constitutional right of equality of treatment.
It agreed with the view of Mr Justice Geoghegan in the High Court when he said: "In the light of the findings of the Dunnes payments tribunal, it is bordering on the absurd to suggest that Mr Haughey is being unfairly or unconstitutionally discriminated against as compared with other ex-Taoisigh, ex-ministers, ex-TDs or as against political par ties or as against other Ansbacher ac count holders.
"The position of Mr Haughey in public life, the nature and amount of the gifts to him by Mr Ben Dunne and the lifestyle evidence, singled him out and he cannot complain, in my view, that he is in some way or other being discriminated as against others."
The Haugheys had also argued the Oireachtas resolutions and the appointment of the tribunal on foot of these were in excess of the jurisdiction of the Oireachtas and the Taoiseach in that they violated the Haugheys' right to fair procedures.
The Supreme Court said the Oireachtas and Taoiseach were entitled to assume the tribunal would conduct its inquiry and all necessary proceedings in relation to it in accordance with fair procedures and the principles of constitutional justice. There was consequently no breach of fair procedures on the part of the Oireachtas or Taoiseach.
It also dismissed a claim that the resolutions and Taoiseach's order violated the constitutional privileges of Mr Haughey as Taoiseach or as a minister. The court said it was clear the parliamentary privilege relates only to utterances made in the Oireachtas and not to acts done or decisions made.
It further rejected a claim that the resolution passed by the Oireachtas was in excess of their jurisdiction because it empowered the tribunal to adjudicate on matters of ethics.
It said the role of the tribunal was not to conduct a trial of Mr Haughey for alleged breaches of ethical behaviour as Taoiseach or as minister nor to adjudicate on such behaviour; its role was to investigate matters of urgent public importance set out in the resolutions of the Oireachtas.
The tribunal was required to make such recommendations as it saw fit. The making of such recommendations did not involve an adjudication on the behaviour, ethical or otherwise, of Mr Haughey.
The court said it saw no constitutional or legal objection to a judge being a member or the sole member of a tribunal, and also rejected the submission that the appointment of Mr Justice Moriarty as sole member of the tribunal was in excess of the Taoiseach's powers on the grounds it constituted an infringement of the constitutional separation of powers.