In some countries (e.g. France) it is illegal to refuse to sell to an individual bona fide customer. That's in addition to the anti-discrimination (race, gender, etc) laws we have in Europe.

So if you sell cakes for €10 and I show up and hand you €10 you are not legally allowed to refuse to sell me that cake. (heads have rolled for less...)

This is pretty effective at preventing discrimination that may otherwise be difficult to prove.