The United States Supreme Court has dealt a decisive blow to the campaign against same-sex marriage in the country by refusing to hear a challenge that would have given anti-same-sex marriage campaigners a chance to argue for the constitutionality of the bans. The refusal to hear the challenge — which has surprised all legal commentators — means that federal (i.e. mid-level) courts can continue to overturn same-sex marriage bans, which means it is likely to wipe out gay marriage bans in another six states.

Confused? So is everyone. But the gist, before we get to the legal meat, is that same-sex marriage advocates have pretty much run out of options. The US Supreme Court hears only a fraction of the cases appealed to it, and only when there is a strong point of law or where a SCOTUS decision would have wide-ranging implications across a range of issues. The court was widely expected to hear the same-sex challenge, since five of its nine members are conservative and have been critical of the idea of implicit rights to marriage equality. They’ve given no reason for their refusal to hear the case (and rarely do in such circumstances).

The new development is the last in a chain of social-cultural lawfare over same-sex marriage. When the concept moved from the fringes to political mainstream in the 1990s, it prompted a strong pushback by the conservatives, in the form of the Defense of Marriage Act (DOMA), 1996 — which was signed into law by Bill Clinton, who was unwilling to be outflanked to the Right on social issues.

However, in June last year, part of DOMA — the crucial bit, limiting marriage to opposite-sex couples — was struck down in a 5-4 decision (US v Windsor), with the swing Justice, Anthony Kennedy, joining the four liberal justices to say that bans on same-sex marriage violated rights to equal protection under the law. But it didn’t go further than that to find that the constitution had an implicit guarantee of the right to same-sex marriage.

What it did say was that states that had ceased to defend their anti-gay marriage laws against challenges in federal courts (i.e. the layer of court between states and the Supreme Court) could not have that defence taken up by third parties. This effectively confirmed the striking-down of anti-same-sex marriage laws in Utah, Virginia, Wisconsin, Oklahoma and Indiana. It also means that those federal court decisions will be taken up by federal courts overseeing challenges to such law in six other states. With those states in the mix (West Virginia, the Carolinas, Colorado, Kansas and Wyoming) same-sex marriage will become legal in 30 states — surpassing a majority, and on the way to a clean sweep of the board.

Things moved fast once the refusal to hear was announced, with clerks issuing marriage licences to same-sex couples in Virginia barely an hour after the decision had been announced. Legally speaking, the same-sex marriage movement isn’t out of the woods (closet? No Rundle, just go with woods, don’t make trouble) yet, since challenges to other state bans on same-sex marriage are being conducted in different federal courts, on different bases. Should the opposition movement have a win there, SCOTUS might have no choice but to hear an appeal, in order to sort out some consistency. But the refusal to hear is the strongest indication yet that the Supremes believe the matter to be dealt with. Most likely, it’s a hedged bet by the four conservatives, who didn’t want the implied constitutional protection of same-sex marriage opened up, since that might open up a whole new field of implied rights over gender, sexuality and much more.

Closer to home, its effect will be crucial. Now same-sex marriage will be the norm in the two great countries of the Anglosphere, the US and the UK, as well as Canada and New Zealand. The pressure will now be on for Australian Opposition Leader Bill Shorten to stand up to his antediluvian Catholic Right and make it ALP policy, and on PM Tony Abbott to allow David Leyonhjelm’s bill to go through and put it to a conscience vote. Otherwise we’ll … oh dear, what can you say? Australia. We are what we are.