Arizona’s highest court is set to decide whether a Phoenix law aimed at prohibiting businesses from discriminating against LGBTQ people violates the state’s constitution.

The case centers on two Phoenix business owners who say designing wedding invitations for same sex weddings goes against their religious beliefs. They argue Phoenix’s non-discrimination therefore violates their free speech.

Joanna Duka and Breanna Koski who run Brush & Nib Studio say they have no qualms with serving gay customers, but designing a wedding invitation that condones same sex marriage is against their belief that marriage is only between a man and a woman.

The Scottsdale-based conservative advocacy group Alliance Defending Freedom (ADF) is representing them at the Arizona Supreme Court.

“The rules should go the same way for other people,” said ADF attorney Jonathan Scruggs. “The government should not be forcing an LGBT web designer to create a website criticizing same sex marriage for a church, or to force a Muslim printer to design and create pamphlets promoting a synagogue’s religious service.”

The case is preemptive and doesn’t involve an actual incident.

Scruggs says the business has pending requests to make such invitations and the Phoenix law carries steep fines and possible prison time.

Earlier this year, the Arizona Court of Appeals ruled against the two women and upheld Phoenix’s ordinance.

“They want the court system to give them a blank check to refuse service to any same sex couple that is requesting custom wedding products,” said attorney Eric Fraser who is representing Phoenix.

“There is no principled way to distinguish between discrimination on the basis on sexual orientation versus discrimination on other bases such as race or even religion.”

Fraser said the city’s law doesn’t force the business to design messages proclaiming support for gay marriage, only to make the “standard wedding invitations that are otherwise identical to what they would make for a straight couple.”

The court’s ruling will likely affect other cities in Arizona with similar laws like Tucson and Flagstaff.

Oral arguments are scheduled for next year.

EDITOR'S NOTE: A previous version of this story said oral arguments are next month. They are next year.