Unless it is overturned in the Supreme Court, Mr Justice Kearns's judgment is likely to encourage a flow of "copycat" cases by people who are unhappy with the tribunal's investigations into their private affairs.
It will inevitably lead to further delays and complications for the Flood tribunal, which is already proceeding at a snail's pace. More than 600 days after it was established, the tribunal has yet to issue an opening statement and to complete the Gogarty "strand" of its investigations.
Meanwhile, its attempts to get two other strands up and running are currently being stymied in the courts. First, the Criminal Assets Bureau has seized documents belonging to the former Dublin assistant city and county manager, Mr George Redmond, and is refusing to give copies to the tribunal.
The tribunal won Thursday's High Court battle with CAB, but the bureau is appealing that judgment to the Supreme Court. Even if the judgment is upheld, the question of whether the tribunal should be given access to the Redmond files would have to be decided by Mr Justice Flood. A further challenge by CAB to whatever decision the chairman might reach on the issue cannot be ruled out.
The final strand of the tribunal's investigation relates to allegations by the Luton-based property developer, Mr Tom Gilmartin. He has made various allegations about Mr Lawlor, as well as alleging that he gave the EU Commissioner, Mr Padraig Flynn, a cheque for £50,000.
Yesterday's ruling severely impairs this line of inquiry, for the moment at least. In challenging the tribunal's right to compel him to attend for interview, Mr Lawlor argued successfully that he had a right to know the allegations being made against him beforehand.
Mr Justice Kearns granted his application to quash two tribunal orders directing him to appear before its lawyers in private session to answer questions, and to swear an affidavit detailing any companies in which he had an interest between 1987 and 1994.
But the judge refused Mr Lawlor's application to quash a third order directing him to produce documents covering payments made to him by Arlington Securities plc and/or Mr Thomas Gilmartin, and other documents regarding his bank/building society accounts between 1987 and 1994.
Responding to the judgment yesterday, Mr Lawlor insisted he had co-operated with the tribunal in every way. If the tribunal wrote to him with allegations against him, he would address them. "They blatantly refused to do that," he told RTE radio.
It was "absolutely outrageous" what had happened to him. The tribunal barristers believed they did not have to comply with High Court guidelines, and now they intended to waste taxpayers' money by going to the Supreme Court, he said.
Ever the political survivor, Mr Lawlor has gained his reward for daring to go where others feared to tread. He was the only one of a group of councillors elected in the mid-1980s who turned down the tribunal's order to attend for interview.
Others went to Dublin Castle reluctantly, and some wish they had not. But only Mr Lawlor faced the tribunal down. A successful businessman as well as a politician, he perhaps felt strong enough financially to risk a High Court action and employ a leading senior counsel, Mr Adrian Hardiman.
Contrast that to the situation in which the former minister for foreign affairs, Mr Ray Burke, finds himself. Despite his bluff reputation and his efforts to avoid a tribunal while still in office, Mr Burke has for the most part co-operated dutifully with the Flood tribunal.
Mr Burke is hardly broke, but concern for the mounting legal costs has played a large part in determining his attitude to the tribunal. His original "A-team" of lawyers has long departed, to be replaced by a more modestly priced team.
His lawyers will be studying the Lawlor judgment closely, but there is no reason to believe his evidence will not go ahead as planned next week.
The former JMSE director, Mr Gay Grehan, will also be studying the ruling closely. Mr Grehan is the man who tipped off the Tanaiste in 1997 about rumours circulating about a payment by JMSE to Mr Burke.
Mr Grehan was interviewed by tribunal lawyers late last year. However, there were major differences between the statement the lawyers drew up based on that interview and a statement Mr Grehan later furnished through his solicitor.
In the witness-box, Mr Grehan was cross-examined about the circumstances of his interview with the lawyers. It was, in effect, his word against that of the two lawyers. The procedure was a shambles.
There is a tussle at the heart of the tribunal which remains unresolved. One side, most eloquently Mr Garrett Cooney SC, for JMSE, sees the inquiry as akin to a trial, where someone is going to be found guilty or exonerated.
Mr Justice Flood, however, says his work is simply to ascertain facts. No one is on trial. His lawyers regard themselves as closer to US-style investigators than Irish barristers.
The Lawlor judgment represents a victory for the traditionalists. It clips the wings of the would-be Eliot Nesses of the Irish Bar and insists that the chairman be present when witnesses are being cross-examined.
The ruling brings to an end a run of courtroom victories for the tribunal this year, in cases brought by Mr Redmond and JMSE. A series of High Court rulings has served to define the extent of the tribunal's powers. Now, finally, the limits to those powers are being imposed.