I soooooo don't understand the difference between the ACT and NT and the rest.
Basically, each state is sovereign, having freely joined the Australian Commonwealth, and state legislative powers are constitutionally protected; Commonwealth legislation only affects states where permitted by the constitution.
Territories, on the other hand, are directly administered by the federal government. Self-government has been granted to the ACT and NT (and Norfolk Island too) by the Commonwealth, but the federal government can override any territorial legislation and has full power to legislate for territories on any issue. The Commonwealth also has direct control over some issues in territories that it does not control in states (e.g. administration of Aboriginal lands in NT).
So basically, had the High Court ruled the ACT's marriage equality act constitutional, the federal government
could have chosen to override it (though I think this would have had to have been via an act of parliament, which would've been unpopular and likely to fail). However, had this been a state marriage equality act and it had been ruled constitutional, the federal government would have been powerless to change it.
As it stands, the High Court's ruling indicates any state-based legislation for marriage equality would be unconstitutional too.
ah that blows.. but couldn't they have figured out this was bound to happen in advance then?
Well it really seems to have been a test case - marriage equality had failed federally, so could a state or territory get legislation up? Could a lawyer provide a convincingly creative reading of the federal Marriage Act (e.g. that the act only covers heterosexual marriage, not homosexual marriage, so states/territories are free to legislate on the latter)? It was always going to be an uphill battle, especially as the Marriage Act was created in the first place to stop a confusing proliferation of different state regulations for marriage.
I do wish that a state rather than the ACT had been the first to go to court, given their stronger legislative position, but in the end I don't think it would have affected the outcome given the court's justification for the ruling.
I truly wonder how they'd respond, since they always ask if you're married or whatnot.
They thought, realised I just mirrored their own argument, and left. 
Better not tell him that there's plenty of animal species that have homosexuality then... becuase they're obviously supposed to be extinct.
