Alberta’s teachers say they will obey a new provincial law forcing them back to work, but are condemning the government’s use of the Charter’s notwithstanding clause to end their strike.

The Alberta Teachers’ Association (ATA) said Tuesday the decision by Premier Danielle Smith’s government to invoke the clause represents what it called a serious misuse of legislative power. The union said it will explore all possible legal avenues to contest the bill, which was passed early Tuesday morning to mandate a return to classrooms.

More than 740,000 students have been out of school for three weeks amid the provincewide walkout. The government says teachers are expected to resume classes by Wednesday. Under the new law, teachers who refuse could face fines of up to $500 per day, while the union could be penalized up to $500,000 daily.

Premier Smith defended the legislation, saying the length and scale of the strike — the largest in Alberta’s history — were harming students’ education and well-being. She said the use of the notwithstanding clause was necessary to ensure a prompt resolution and prevent court delays.

The ATA says the dispute is far from over and hopes other unions will support its effort to challenge the government’s action.