Baronelle Stutzman was sued after she declined an order from a customer she had previously served for ten years,
The US Supreme Court has asked the Washington Supreme Court to reconsider the lawsuit in light of the recent decision given to cake-maker Jack Phillips who won a case in which he was told he was within his rights to refuse to make a cake for a gay wedding.
The country's top judges ruled 7-2 in his favour.
Stutzman is being represented by religious freedom charity Alliance Defending Freedom (ADF).
Addressing the development, ADF senior vice president of US legal division Kristen Waggoner said: "Barronelle, like Jack, serves all customers but declines to create custom art that expresses messages or celebrates events in conflict with her deeply held religious beliefs.
"The Washington attorney general's efforts to punish her because he dislikes her beliefs about marriage are as impermissible as Colorado's attempt to punish Jack.
"The US Supreme Court has rightfully asked the Washington Supreme Court to reconsider Barronelle's case in light of the Masterpiece Cakeshop decision.
"In that ruling, the US Supreme Court denounced government hostility toward the religious beliefs about marriage held by creative professionals like Jack and Barronelle. The state of Washington, acting through its attorney general, has shown similar hostility here."
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