The #carbontax proceedings at the Supreme Court of Canada are now under half an hour away. The main legal issue concerns scope of what the federal gov't can regulate under what's called the "national concern branch of POGG". Major precedent on federalism. Watch here for updates.

And the #carbontax proceedings are underway, with the new two-row social distancing format for the justices (and yes I am enough of a constitutional law nerd to project the webcast on my wall (while working on my computer)!)

About 15 minutes in and there have now been questions from 5 different justices (Brown and Abella kicked things off, but others have joined in) - lots of thinking going on about effects of the backstop, whether feds can impose national stds, etc - fascinating discussion ahead

Justice Brown points out the significance of understanding the question even more precisely - not which gov't makes a decision on greenhouse gas policy but whether the particular means chosen by Parliament are ultra vires (outside powers of federal Parliament)

Second Saskatchewan counsel now up and boldly arguing that "national concern branch" of POGG is not even a constitutionally authorized power (referencing some of the Alberta CA decision). [This case has major implications for federalism in many ways.]

Lengthy pushback from Justice Moldaver about the existential threat of climate change, international treaties, and systemic problems.

(I note that there are other live twitter feeds giving every detail - right down to when counsel has a sip of water - I'm going to just highlight some of the key developments when I can and try to offer some perspective on what they mean).

Saskatchewan's lead argument is already done - fast-moving, almost fiery hearing with justices actively intervening and at times seeming to try to answer each others' questions [I think it's getting safe already to predict a divided bench]

Rowe, amid commenting on some "gobbledygook" in the statutory phrasing, shows an ongoing interest in the issue of the permissibility of the federal gov't enacting national standards

A number of detailed questions to Ontario counsel. Kasirer, speaking for just second time in the hearing, has now asked how the principle of subsidiarity might have a role in the POGG test - Ontario connects to broader concerns of federalism

Karakatsanis is now in a detailed parsing of specific paragraphs in the language of Justice LeDain's judgment in the Crown Zellerbach precedent - the Court may ultimately say some very interesting things on the precise meaning of the POGG tests

Court returned from morning coffee break to hear now from British Columbia (which defends the federal law). Justice Rowe puts a forceful challenge, suggesting the supervisory character of the law does not fit the idea of what POGG was meant to encompass.

Court back from lunch, hearing from AG Canada, with Justice Cote (sorry I don't have accents easily here) early probing the "evolving" characterization of the pith and substance of the law in the AG Canada's arguments over time

There had been some recent controversy about the federal gov't dropping its own Justice lawyers and hiring outside counsel Guy Pratte to argue their case at the SCC. But he is a very experienced advocate and it shows. Doesn't change the law, but puts a best foot forward.

Kasirer asking some interesting questions on how Pratte's theories fit/don't fit with past statements in various cases (including whether he would effectively reverse the conclusion in the Anti-Inflation Reference, which would be a problem for his theory)

Pratte into difficulties trying to claim that carbon taxes are "the essential tool" in order to reduce greenhouse gases (vs judges clearly thinking they are one of various possible tools)

Counsel for Alberta emphasizing need for sufficient constraints on POGG power - Martin pressing on details of legal test and asking to what degree should follow reasoning from the Alberta Court of Appeal (eg on 92(16))

Alberta counsel challenging BC's proposed proportionality analysis as inappropriate for division of powers issues, expressing concerns about whether law on POGG will be such as to allow provinces to plan

Day wraps up on a slightly confusing note about what pages of written materials are being discussed. But an action-packed day overall! (Intervener parties tomorrow, starting with Quebec arguing vs the carbon tax due to concern for precedent on jurisdictional rules)