A sign doesn’t stop you from being bound by the same laws as everyone else.
...it might prevail in court, depending of course on the attorneys and the judge...but we could make book that an appellate court would be involved, sooner rather than later...
I don’t think even lower court judges would rule in favor of the business owner in that case. Those cases already wound their way through the system decades ago, so the precedents are too solid for anyone but the Supremes to challenge them now.