Unless, of course, you are Bill Clinton giving a campaign speech in a Black church...
That would be a violation of the priests free speech, and possibly the Catholic Church's right to free assembly, though I am not an expert in Constitutional Law.
But mark my words, someone will eventually sue the church for "violating their right to religious expression" because the church is keeping them out on account of an unrepentant sin. And who can doubt that they will find a sympathetic judge who wants to nail Christianity?