The NSW Nurses and Midwives' Association is facing possible court-ordered penalties in a case filed by the state government over strikes in February and March 2022.
In the NSW Supreme Court lawsuit, the secretary of the NSW Ministry of Health claims the protests breached orders made by the state's Industrial Relations Commission which ordered the union to stop its planned industrial activity.
The IRC made two separate orders on February 14 and March 25 that the union cease organising strike action or encouraging its members to take part.
Statewide protests still took place on February 15 and March 28 to demand safe staffing levels and higher nurse-to-patient ratios in the state's public health system.
"Remember, while the Association can be fined for not complying with a dispute order made by the IRC, individual members are not targeted for fines," the union wrote in an email to members on March 25.
"The NSWNMA Council supports democratic action members choose to take in pursuit of safe staffing. It's time to hold strong, continue the fight and attend your rally as planned."
The March protests took place in more than 20 locations across NSW and involved over 160 branches of the union voting to walk out.
The nurses' union has been approached for comment.