Only a few months ago Prime Minister Stephen Harper would not even tell the House of Commons whether he still believed - as he argued as a leading Reform party critic at the time of the 1995 referendum - that a simple majority in favour of sovereignty in Quebec could be enough to negotiate the province's secession from Canada.
Now federal lawyers acting on his orders are headed to court to challenge Quebec's contention that it can leave the federation on the basis of a 50-per-cent-plus-one mandate.
What is one to make of this apparent change of tack?
The first conclusion that jumps to mind is that the federal government is taking the possibility of another referendum showdown in Quebec more seriously than it has in more than a decade.
That's how long this provincial law has sat on the books unchallenged by Ottawa.
The other is that Harper is taking the Liberals under Justin Trudeau more seriously than in the recent past.
But first a refresher: Bill 99, the provincial law at the centre of the looming legal battle, was PQ premier Lucien Bouchard's chosen instrument to mobilize Quebecers against the 2000 federal Clarity Act.
The Quebec law affirms that the national assembly alone set the terms under which the province would leave the federation.
Its basic contention is that their right to self-determination trumps the Canadian constitutional order.
As a political gesture, it essentially failed. In the national assembly the opposition Liberals under Jean Charest refused to support it. (As a Liberal MNA, New Democrat Leader Thomas Mulcair voted against the bill.)
By the time it was passed in late 2000, Quebecers had indirectly pronounced on the federal Clarity Act but not in the way Bouchard had hoped.
Jean Chrétien's decision to spell out the conditions under which a future Canadian government would engage in secession talks with Quebec was front and centre in a federal election held that same fall.
When the votes were tallied, the Liberals had beaten the Bloc Québécois in the popular vote for the first time ever. The result prompted Bouchard's departure from politics a few months later.
As a law, Bill 99 has yet to be tested in court. It took 14 years for a handful of English-rights activists to get a date to argue their case that it should be struck down because it is unconstitutional.
That speaks volumes about the obscure status the Quebec law enjoyed until news that the federal government had added its voice to the challenge broke in a Maclean's exclusive on Friday.
Perhaps only in Canada is it considered more surprising that the country's justice department would defend a fundamental federal law than the opposite.
The section of Bill 99 that sets the threshold for a secession mandate at 50 per cent plus one is among those that the Harper government is specifically challenging.
It is a threshold that Harper defended in his Reform days. But then at the time he also opposed the recognition of Quebec's distinct status and that did not stop him from putting forward the nation resolution a decade later.
With this latest prime ministerial change of heart, very little now distinguishes Harper's approach to the Quebec secession debate from that of Chrétien or at least from Chrétien's post-referendum stance.
In 1995 the Liberal prime minister was unprepared for a potential sovereigntist referendum victory.
Harper has other, more partisan, reasons to be seen to pre-emptively gear up for a possible resurgence of the Quebec-Canada debate.
Under the scenario of a PQ majority election victory, the prime minister would have to worry about being blindsided by Trudeau.
For scores of voters the Liberal party - because it was in government at the time of the 1980 and 1995 referendums - owns the unity issue.
A final word: since Friday there has been a chorus of federalist complaints that Harper is providing premier Pauline Marois with timely ammunition to take into a possible election campaign next month.
In fact, since 1995 the PQ has tended to lose ground whenever it has been forced to spend time waxing about its professed goal of another referendum.
Chantal Hébert is a national affairs writer. Her column appears Tuesday, Thursday and Saturday.