One has to understand contract law to understand the legality of this....

Remember, you can not change to rule/conditions of a contract in the middle unless both parties agree to the changes.

When I was growing up...many moons ago...business's had sign's over/on their door that read 'We reserve the right to reserve service to anyone for any reason'.

This establishes the rules of contract BEFORE you enter into the business, thus you agree to the terms..

You see restaurants with their 'no shoes, no shirt, no service' signs all the time

I think of this everytime I hear of those who are forced to perform a service against their will. If those bakers had this sign on their front door, their case would have been thrown out of court...cause they don't want the public to learn the truth.