A Christian baker is appealing a 2021 ruling that found him guilty of discrimination for refusing to bake a cake celebrating a gender transition. 

Jack Phillips, owner of Masterpiece Cakeshop in Colorado, refused the order for a cake in the pink and blue colours of the transgender flag. 

The order for the cake was made in 2017 by a Denver-based transgender lawyer, Autumn Scardina, who had recently transitioned.

Last year, the court found that Phillips violated Colorado's anti-discrimination law in refusing Scardina's order on the basis of Scardina's gender status. 

Phillips this week returned to court with his lawyers from the Alliance Defending Freedom asking that the 2021 ruling against him be overturned and that his free speech rights be upheld. 

"No one should be forced to express a message that violates their beliefs and conscience," said ADF Senior Counsel Jake Warner, who represented Phillips at Wednesday's hearing.

"Activists and state laws have threatened artists like Jack and graphic artist Lorie Smith because they can't express messages on marriage and gender that violate their core beliefs.

"In this case, an activist attorney demanded that Jack create expressive cakes to test him and 'correct the errors' of his thinking.

"The attorney even promised to sue Jack again if the case is dismissed for any reason. Free speech is for everyone.

"The Constitution protects the freedom of every American to express ideas even if the government disagrees with those ideas."

Phillips previously won a partial Supreme Court victory after refusing to bake a same-sex wedding cake in 2012. The Supreme Court found that in being penalized by the state of Colorado, his First Amendment rights had been violated.