- That companies (plural) stop selling gas. That's coordinated action, because you need all the oil companies (or all the gas stations) to agree.
- That the government decides it. But in a democracy, that takes coordinated action too. The president does not have the constitutional authority to decree "no more sales of gasoline for passenger vehicles".
Let me put it this way: why do you think there isn't an OPEC-like private marketplace for uranium? Because states don't want there to be such a thing. States make themselves an oligopsony for the purchase of uranium, and then regulate its distribution to only parties they want to have it. And people generally like it that way.
(Also, the president of the United States is a bad example of what a country's executive's powers generally are, because federalism. Most other heads of states can just make a decree like that.)
But state action is a less-likely scenario, and also not the one I was really imagining. The more likely scenario is local action — i.e. a mayor enacting a bylaw for their municipality such that gas stations that don't regulate sale of gasoline would be blocked from operating within city limits. (And sure, you could drive outside the city limits to get gas... but presuming the metropolitan area is large enough, you might burn the whole tank just getting back home after doing that.)
A mayor does have that power. They need no referendum, no legislature, to pass such a bylaw. They merely need the people to be okay-enough with the action to not impeach them in response. (In fact, technically, you don't even need the bylaw. Businesses only operate on physical commercially-zoned properties in cities at the city's sufferance; a city government is free to revoke a given business's ability to operate on such property at any time, for no reason. A city can un-make the zone a business is operating under, and replace it with a new zone that has different rules, that then exclude that business. This happens all the time!)
From there, it spreads not by coordinated action, but just by other city governments seeing the idea and copying it.
California, Maryland, Massachusetts, New Jersey, New York, Oregon, and Washington are going for it: https://www.cnet.com/roadshow/news/states-banning-new-gas-po...
https://energyandcleanair.org/publication/china-permits-two-...
A ton of people now have vehicles that are basically scrap metal, they've lost tens of thousands overnight. There are physically not enough EVs, or charging infrastructure, or maybe even the grid capacity in order for people to switch.
By 10am, immigration lawyers' phones around the world are off the hook.
If you phase it, then you're just describing what is already happening, this is what coordinated action looks like.
A country could do it; or it could be done city by city with municipal bylaws to act only upon the worst polluting regions. And, since the only restriction would be on buying gasoline, people who still wanted to drive could just buy EVs.