DENVER (AP) -

A gay couple is pursuing a discrimination complaint against a Colorado bakery, saying the business refused them a wedding cake to honor their Massachusetts ceremony.

It's a case that highlights a growing tension between gay rights advocates and supporters of religious freedom as more states move to legalize same-sex marriage and civil unions.
    
The Colorado Attorney General's office filed a formal complaint last week after the ACLU initiated the process last year on behalf of David Mullins and Charlie Craig. They say Masterpiece Cakeshop in suburban Denver refused to make a cake for them when they told the owner it was to celebrate their Massachusetts wedding in a reception in Colorado.
    
Attorney Nicolle Martin, who is representing the shop owner, says it's a case about honoring people's religious beliefs.