The sale of Hydro One shares is now before the courts.
The Canadian Union of Public Employees warned the government two months ago it was prepared to sue and it's followed through, filing the lawsuit yesterday.
So far, half of the province's 60 per cent goal has been sold.
President Fred Hahn is sounding the alarm that sales of Hydro One shares need to be stopped before it's too late and the effects are felt for generations to come.
"Today we still own a majority of Hydro One and there is still accountability to our government. The minute we lose majority control, decisions about the electrical system will be controlled by a corporate board whose soul interest is to raise profit and not the interests of the people."
The province now has up to 30 days to file its response.
Hahn says CUPE expects the government to suspend the selling of shares while the matter makes its way through the court.
CUPE's lawyer Darrell Brown explains an injuction is very difficult to get. "We haven't asked for an injunction. It's a very high bar to obtain an injunction. Basically, you have to demonstrate there would be irreparable harm and you can't obtain damages that would compensate."
He says it could still be an option in the future.
WATCH: CUPE taking the Wynne Liberals to court over the sale of Hydro One shares. #onpoli pic.twitter.com/Lj6aJMTwMU
— NEWSTALK1010 (@NEWSTALK1010) December 7, 2016