leady wrote:this is where my understanding of the US system fails (largely from the west wing) but surely gay marriage isn't a constitutional change just a federal law? or are there restrictions on what federal laws can be passed?
The constitution is the top tier of federal law. Underneath it are a bunch of various laws passed by congress. Under that, there's various non-law regulations passed by this agency or that(which trace back to authority given via one of the above). There's also the state branch, which is similar, and mostly under federal...but this can get complicated. This is all a HUGE simplification.
SCOTUS can decide that something is unconstitutional, and if that's the case, well...that's kind of a trump card, barring an explicit amendment to the constitution, which is really difficult to do.
There are constitutional protections regarding equality that generally support the gay rights case, but I haven't delved through the legalese to see what all arguments have explicitly been made in this case. Given that DOMA was struck down as unconstitutional, there's effectively no legislative recourse available short of
A. denying marriages altogether
B. a constitutional amendment.
Both face severe practical difficulties, so on a federal level, this pretty much settles things, though I expect stubborn states to dig in their heels, create further bad situations, and to then lose subsequent lawsuits hard.