Assembly pass gay marriage, but DUP veto.
Why?
The DUP have a veto because they posted a "petition of concern" which allows a motion to pass only if it obtains a majority of both Unionists and Nationalists in support.
The mechanism was originally designed to prevent one side forcing through legislation over the heads of the other, but it now tends to be used by both larger parties to prevent anything inconvenient to either of them getting passed.
Only four Unionists voted in favour of the motion - three independent unionists (McCrea, McCallister and Sugden) who have always voted in favour plus one newly co-opted Ulster Unionist (Allen). This doesn't represent a major shift in opinion on the Unionist side; one Unionist who voted in favour of it last year (Kinahan) has left the Assembly on his election as an MP, and the UUP leader (Nesbitt) abstained.
What made the difference is that a couple of the more socially-conservative Alliance members (Lunn and Cochrane) voted in favour this year, having voted No abstained last year.
I think this will make FFs plans of entering Northern politics more realistic. There should be a (although relatively small) market for a SoCon centre-right option among Catholics. This vote could be the opening.