No it wouldn't get by. This exact practice has been ruled discriminatory in several cases. Several restaurants throughout the US over the past decade have found out that offering "10% off meal on Sunday's, when you bring in today's church bulletin" is a fast way to get a lawsuit happening and all of them have been forced to stop it. Offer 10% off to everybody or to nobody, but you can't offer pubic services to one group (Christians) and not the same to another group (anyone else who doesn't attend Sunday church) unless you're a private club. Again, it's a matter that if you offer something to the public, you can't pull this sort of discriminatory shenanigans.