The United Nurses of Alberta has filed a statement of claim saying Bill 45, which bans strikes by some unions, violates freedoms guaranteed under the Charter of Rights.
The union, which represents almost 30,000 registered nurses and other health staff, has asked the Court of Queen's Bench to throw out parts of the law.
Meanwhile, the Alberta Union of Provincial Employees is heading to the labour relations board to challenge Bill 46, which could impose a contract on 22,000 government workers.
Union president Guy Smith says the law amounts to unfair bargaining.
Government workers in Alberta have not had the legal right to strike since 1977, but until last month had the right to send contract deadlocks to binding arbitration.
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