May law or government policy be based on faith? Given our nation's secular tradition, we would rightly protest a law prohibiting any person to eat pork merely because pork consumption is forbidden by some interpretations of the Bible. Any law based solely on sectarian religious belief should be rejected out-of-hand in a democratic society.
The objection is not that this law abridges the free exercise of religion. To the best of my knowledge, not eating pork does not violate anyone's religion. Rather, it must be rejected because it serves no legitimate public purpose and simply imposes one group's religious faith on the nation as a whole. Whether or not such a law violates the First Amendment's Establishment Clause ("Congress shall make no law respecting an establishment of religion"), it certainly undermines a fundamental precept of American democracy -- one person's freedom should not be infringed merely to satisfy another's religious faith.
It turns out that in California, eating pork is perfectly permissible -- but selling horsemeat for human consumption is illegal. There are similar laws in other states; some states also ban the sale of dog for human consumption.
To my knowledge, the reason for this isn't protecting public health or preventing cruelty to animals (slaughtering horses for animal consumption remains completely legal). Rather, it's that -- in the words of one activist -- eating horse is "morally perverse," "a perversion of the human-animal bond." People find eating horse to be disgusting, immoral, perverted.
So this law "simply imposes one group's [moral] faith on the [state] as a whole." The majority thinks people shouldn't eat horses, so they constrain the minority. That's the way democracy works.
Why is banning horsemeat for secular moral reasons -- unproven, unprovable, visceral -- OK, but banning pork for religious reasons forbidden? What if it turns out that some people who back the ban on horsemeat do so for religious reasons? (Horsemeat is also not kosher, and apparently in the Middle Ages some Christian leaders believed that eating horsemeat was religiously prohibited.) Would an otherwise permissible law (permissible because it was backed by people who derive their morality from secular gut feelings) become impermissible because it would now be backed by people who derive their morality from religious beliefs?
It seems to me that the answer is no: The Establishment Clause may properly be read as barring government speech that endorses religion, or government action that treats people differently based on their religion, or even government action that is aimed at promoting the teaching of one or another religion. But when it comes to laws that regulate secular actions (even including food consumption), it shouldn't matter whether the law's backers are motivated by religion or by secular moral axioms and gut feelings. A contrary rule would discriminate against voters and lawmakers because of their religiosity.
Of course, one can criticize the bans on eating pork and horse on libertarian reasons: People should be free to eat whatever animals they please, the argument would go, and others' revulsion is no reason to constrain what people choose to put into their own bodies. But that's an argument that (rightly) focuses on whether the law -- which could be motivated either by religion or by secular morality -- interferes with people's liberty, rather than (wrongly) focusing on whether the law's backers support it for religious reasons or for secular moral reasons.
I elaborate on this more in this thread. But even without the elaboration, I hope the pork/horse analogy helps illustrate my point: If California may ban horsemeat, why can't a hypothetical majority observant Jewish state ban pork meat?