You never know which person or organisation or action will fall victim to his excoriating wit - you just hope it's not going to be you.
Often he praises.
In a speech recently to an international body of legal arbitrators, he was full of praise first for the important role the Waitangi Tribunal played in New Zealand as a permanent commission of inquiry.
He praised, too, former Labour MPs-turned-Crown negotiators; officials in the Office of Treaty Settlements, whom he described as the "Jesuits'' of the public service; and the post-settlement commitment unit in the Ministry of Justice.
It's a means by which the Government can keep track of all the commitments it has made in the mounting number of settlements it has negotiated.
There is a lot for New Zealand to be proud of in terms of its treaty settlements.
Mr Finlayson has rightly earned respect across the House for his drive in trying to get a settlement with every iwi that has a mandate.
But his address to the visitors didn't mention the first settlement, the 1992 Maori commercial fisheries settlement.
Why would he when the parties to it are in dispute over the proposed Kermadec Ocean Sanctuary, 1000km north of New Zealand?
It promises to be a significant battle because of the principles and the players involved.
About two weeks ago Te Ohu Kaimoana (Te Ohu), the Maori fisheries commission, filed a claim in the High Court at Wellington over the Government's plan to turn the sea around the Kermadec Islands into an enormous ocean sanctuary taking in the 200 nautical-mile EEZ.
The Bill setting up the sanctuary extinguishes Te Ohu's fishing rights in the area, a decision made with no consultation and no compensation.
The Cabinet decided that while Te Ohu held fishing rights by dint of the 1992 fisheries settlement, it was not entitled to compensation because it had not used the right to fish for its quota.
Te Ohu chairman Jamie Tuuta, one of the new generation of Maori leaders, told the annual conference this week that an analogy would be if someone owned a vacant lot in central Auckland, left it unused and the Government came along and said "you haven't used it so we're taking it for the Auckland housing crisis''.
Te Ohu is responsible for administering the assets of the 1992 Maori fisheries settlement.
Importantly, the fisheries deal was founded on a deed of settlement among all tribes, a document which has acquired the status of a constitutional one among iwi leaders.
The fisheries settlement was negotiated with all tribes together, a pan-tribal deal, quite different from the iwi-by-iwi settlements of today.
It was horrendously difficult to achieve, momentous and enduring, until now.
Sir Tipene O'Regan and Sir Graham Latimer are among the surviving leaders who negotiated with Sir Douglas Graham and the Bolger government.
The Government expected it to be a full and final settlement as it does now.
To Ohu was entitled to expect the same.
It could be a very long battle; the iwi representatives at Te Ohu's annual meeting this week had been planning to approve a restructuring that would have dispersed a $74million fund to its 58 constituent iwi.
But they voted without dissent to delay the dispersal, to keep the $74million intact as the basis of a war chest until the Kermadec case has been resolved.
It is not going to be a popular cause - the Kermadec Sanctuary Bill had unanimous support of all parties to select committee, although Act New Zealand has major misgivings about the lack of compensation.
This case is less about the compensation and more about the failure of the Government to uphold what is essentially the mother of all treaty settlements.
There are always disputes going on between Maori and the Government, although some disputes can give others a bad name.
Opponents of the TPP spent a week in the Waitangi Tribunal recently explaining how in their view it breached the Treaty of Waitangi, despite the TPP having a specific clause allowing more favourable treatment for Maori so the Government can meet its Treaty of Waitangi obligations.
In another dispute, a group which opposes changes to laws governing Maori land, Te Ture Whenua Act 1993, sent a complaint this week to the UN's High Commissioner of Human Rights claiming the Government has breached the UN Declaration on the Rights of Indigenous Peoples, which John Key's Government signed in 2010.
New Zealand's commitment to the Declaration on the Rights of Indigenous Peoples was a big deal at the time.
Former Maori Affairs minister Pita Sharples made a very hush-hush visit to the UN to make the surprise announcement.
Something similar happened with the Kermadec decision.
Mr Key wanted to make the announcement during leaders' week at the United Nations last September.
There were two reasons for the plan to be kept tight. He wanted the element of surprise to maximise the splash and kudos.
The sort of consultation that would normally have gone on with affected parties before a decision did not take place.
And the Government did not want to risk the possibility of Te Ohu finding out about it in advance and opposing it.
Secrecy was paramount.
The imperative for political impact drove the departure from good process.
Environment Minister Nick Smith wrote his own Cabinet paper.
Officials were not required to write a regulatory impact statement, a document that outlines the effects, until after the decision was announced.
The chairman of Te Ohu Kaimoana was notified just hours before Mr Key's speech, as were two northern iwi closest to the Kermadecs, although Te Ohu holds the property right.
It is a dispute in which Mr Finlayson may be conflicted.
His role as Attorney-general requires him to defend actions of his Government.
But as Treaty Negotiations Minister, notions of "good faith'', "full and final settlement'' and "property rights'' are supposed to mean something.
Unlike many cases pursued by Maori through courts, tribunals and international bodies, this one deserves to be a significant battle.
● Audrey Young is political editor of The New Zealand Herald.
