Gov. Andrew Cuomo is moving ahead with a tristate summit Oct. 17 to seek common policies on marijuana and vaping across New York, New Jersey and Connecticut. But how will the governors and legislators of three states find it any easier to come to a rational consensus than the leaders of each state separately?

Cuomo claims the states are forced to go it alone because the federal government isn’t acting, but that’s not quite right.

On marijuana, the real history is of states gradually defying federal law — and the feds deciding to mainly overlook it.

Pot is still officially banned in the entire country, but decriminalization, medical-marijuana laws in 33 states and now outright “legalization” in 11 states plus the District of Columbia have steadily eroded that.

Federal law still complicates the financing of legal-pot companies, but the Justice Department hasn’t forced any real confrontation over the issue, even under pot-hating former Attorney General Jeff Sessions.

Current AG William Barr has told Congress he favors “one uniform federal rule against marijuana,” but is open to legislation reform “so states can make their own decisions within the framework of a federal law so we’re not just ignoring the enforcement of federal law.”

Meanwhile, both New Jersey and New York have hesitated to fully legalize pot. Last December, Cuomo said he was confident it would happen this year and lead to $1.3 billion a year in new state tax revenue. Jersey’s Gov. Phil Murphy has cited similar figures in his hard push for legalization.

But even with Democrats in total control in both states, it hasn’t happened — thanks to doubts from the left and right about mixing big business and recreational drugs, new concerns about pot’s health impact and battles over splitting up the promised tax windfalls.

As for vaping, Cuomo claims the feds aren’t acting, though the Food and Drug Administration is trying to crack down. The issue’s hopelessly foggy because the sudden wave of vaping deaths seems to involve mainly black-market products, so bans are likely to make the problem worse.

Maybe the summit will somehow bring clarity to all this. More likely, it’ll leave everyone as divided and confused as they are now.