Yup, and it's been the rule for decades, don't blame the current boss man.
Canadians are allowed 120 days per year in USA, or if we file with your IRS and declare a closer connection to another country we are allowed 182 days. It is enforced, our passport is swiped both ways and violators are declared illegal alien, deported, and banned from re-entry for 5 years.
There is also a limit to the number of days a US citizen can spend in Canada. The limit is 180 days, after that you need some sort of visa. I ran into this a few years ago while contemplating buying a lakeside cabin in Ontario. It works both ways.