That grating sound isn't anyone mourning the death of the marriage equality plebiscite. It's the grinding of gears as the opposing forces shift their positions to a new battlefront.

Hardly a surprise that the Prime Minister looked so chipper about this "defeat". The plebiscite is Turnbull's albatross, hung around his neck by an ungrateful Liberal party room and opportunistic National Party as the price of his accession. He has worn it with ill grace.

As Bill Shorten commented, that's not his problem. Whether Labor was motivated by principle or politics, it did the right thing and thank god we can finally move on.

The forces opposed to marriage equality know this is not the end; they'll be needing a new strategy. As ever, the one thing they won't want to argue about is the principle of equality, so a wider field of combat must be engaged. Personally, I think much of the pro-equality camp continues to fall into the trap of fighting the wrong battles, although in the end nobody will remember or care how we got there.

[Plan B from outer space: Turnbull's SSM strategy now relies on hope]

To the main game. Marriage equality will happen, as was always the case, only when federal Parliament votes to amend the Marriage Act to remove John Howard's 2004 insertion, which ensured that marriage would remain an exclusively heterosexual thing.

The principal necessary amendments are straightforward; the words "a man and a woman" are replaced by "two people" in the definition of who can get married. This doesn't affect the prohibitions on bigamous, polygamous, incestuous or under-age marriages, which all remain. There's nothing to see here.

So the focus is shifting to the periphery, as has already been seen in the response to the government's exposure draft of the amending bill it would have been putting before Parliament had the plebiscite gone ahead.

As with actual weddings, most of the controversy concentrates not on the happy couple but on the seating arrangements and the bridesmaids' dresses, along with the increasingly tricky issue of whether the cake should be gluten and dairy free.

[Hinch's Senate Diary: good riddance to a grubby plebiscite]

Which is why attention has fastened on the ancillary bits: if a gay couple can marry, must ministers and celebrants be forced to marry them? And must they be allowed to sit on heterosexual pews, or eat heteronormative cake?

Interesting questions, these. The legal tension arises because it is generally prohibited under anti-discrimination laws to refuse to provide goods or services to a person because of their sexuality. But how is that to be reconciled with conscientious objection on religious grounds? After all, many religions openly consider homosexuality to be an abomination.

The government's answer has four parts. Ministers of religion would be able to refuse to solemnise same-sex marriages on the basis of the "doctrines, tenets or beliefs" of their religion or if their refusal is "necessary to avoid injury to the religious susceptibilities of adherents of that religion". I doubt even God knows what that means.

Civil marriage celebrants may also refuse to marry same-sex couples, if their "conscientious or religious beliefs" get in the way.

The protection for religions doesn't stop there. The draft bill also says that a "religious body or religious organisation" may "refuse to make a facility available or to provide goods or services" for a wedding or anything "reasonably incidental" to it, on the same grounds as a minister can refuse to perform the wedding.

The government has not, however, extended the same "protection" to other suppliers, such as the commercial baker who has a religious objection to putting two men or two women atop one of their wedding cakes.

This compromise is being attacked from both sides, for entrenching legal discrimination and for not sufficiently protecting conscientious objectors.

Whenever law and religious faith collide, irreconcilable differences result. The paradox is precisely why the democratic model of government seeks explicitly to separate Church and state. The US constitution's first amendment prohibits laws "respecting an establishment of religion, or prohibiting the free exercise thereof".

Our own constitution has a less effective version, in language and in the scope the High Court has allowed it. Section 116 prevents laws "for establishing any religion, or for imposing any religious observance, or for prohibiting the free exercise of any religion". The key difference from the US model is that between "respecting" and "for". In the context of the Marriage Act, allowing discrimination against same-sex couples on the basis of religious belief is not likely to be read by the High Court as a law whose purpose is to establish or impose religion on anyone.

[Death of the plebiscite a win for marriage equality]

That means that a constitutional challenge would fail. It doesn't make for good law. The inherent problems with giving legal force to religious belief arise both at the margins of the definition and in the endless scope for application of the identical principle in surprising contexts.

The first obvious question is "what is a religious organisation"? There is no registration process for religions; religion is entirely a matter of personal faith separated from facts or logic, therefore any belief system can be a religion and any gathering of people around that system can be a religious organisation. Homophobia itself, as a personal tenet, would have no less strong a claim to religious status than any other faith. It isn't difficult to appreciate where this might lead.

More importantly, when we start down the path of religious exception, where do we end? In modern society, the original conscientious objection given protection of law was the refusal to go to war on personal ethical grounds. It was extremely controversial, with public sympathy mostly reserved for those who claimed religious sanction (such as Quakers) and opprobrium heaped on personal pacifists. When you think about it, is it more worthy of respect that a person refuses to fight because their religion says they can't, than that their refusal is a matter of their personal conviction?

[Why is the Coalition suddenly making room for `conscientious objectors' in gay marriage debate?]

Anyway, apply the same principle to weddings. We can start with the seemingly simple proposition that nobody should have to conduct a wedding that offends their beliefs, from which we seamlessly move to the church hall not having to host said wedding, or the Hillsong house band not being obliged to play at the reception. But what's the difference between that and the deeply religious provider of table decorations, which can't legally refuse supply simply because they aren't a "religious organisation"? Or, even more pointedly, the difference between that supplier and a civil celebrant? I don't see it.

Then take the same paradox outside the wedding party. Should it be lawful for a church to refuse homosexuals burial in its graveyard? If yes, why shouldn't a commercial funeral director who subscribes to the same church's religion also be able to refuse service on the same basis?

All this has nothing to do with marriage equality, of course. What it really does is illustrate that when equality is treated as a question of (infinitely variable) religious doctrine rather than what it really is, a principle of law, we head quickly into a maze of limitless contradiction.

I'd humbly suggest, if we're going to stick with letting ministers of religions conduct marriage ceremonies, that they be allowed a complete personal discretion to not do so without having to explain why. I'd not extend the same compromised favour to civil celebrants, and I'd say the churches and cake makers should otherwise suck it up. And lighten up; weddings are about love, remember?