TORONTO -- The federal government will end up with the power to regulate almost every facet of life -- such as when you can drive or where you can live -- if its law aimed at curbing harmful greenhouse gas emissions is allowed to stand, Ontario's top court heard Monday.

Ottawa's climate-change law is so broad, a lawyer for the province told the start of a four-day Appeal Court hearing, that it would give the federal government powers that would be destabilizing to Canada in the name of curbing the cumulative effects of global-warming emissions.

"They could regulate where you live. How often you drive your car," Josh Hunter told the five-justice panel. "It would unbalance the federation."

In his submissions, Hunter was categorical that Ontario's constitutional challenge to the federal Greenhouse Gas Pollution Pricing Act was not intended to be a debate on the realities or dangers of global warming. What's at stake, he said, is which level of government has the power to deal with the problem.

"Which measure is the best measure -- the most efficient measure -- is best left for legislatures to decide," Hunter said. "Which legislature? That's what we're here to decide."

The federal government law that kicked in on April 1 imposed a charge on gasoline and other fossil fuels as well as on industrial polluters. The law applies only in those provinces that have no carbon-pricing regime of their own that meets national standards -- Ontario, Manitoba, Saskatchewan and New Brunswick.

The Liberal government, which is due to make its submissions on Tuesday, insists its law is an appropriate response to the nationally important issue of climate change. It maintains the legislation was designed to "fill in the gaps" where provincial measures aren't up to snuff. The aim, the government says, is to cajole people into changing their behaviour.

The federal law, Hunter also said, puts a "tax" on ordinary people every time they drive to work or heat their homes, which he said was too much of a burden.

As the justices pointed out, Ottawa is promising to return the money it collects to people in the affected provinces to offset the charge.

Hunter, however, said the rebates -- via the federal climate action incentive -- flow to everyone in the impacted province regardless of whether they drive at all, for example.

"It's not just that you get back what you give," he said.

Progressive Conservative Premier Doug Ford insists Ontario can curb greenhouse gas emissions on its own and has already taken significant steps to do so.

Those steps, Hunter told the court, include shutting down coal-fired power plants -- a measure in fact taken by the previous Liberal government -- which has sharply reduced the province's harmful emissions.

"Ontario is further ahead than all the other provinces," Hunter said. "(But) none of those (steps) count towards determining whether Ontario has a stringent plan."

In addition, he said, the province is developing a "made in Ontario environmental plan" that is still under consideration.

Fourteen interveners, including provinces such as Saskatchewan and British Columbia, Alberta Conservatives, Indigenous organizations who point out they are acutely vulnerable to global warming, as well as business and environmental groups, will get their say over the course of the hearing.