In 2004 Nicola Roxon and Philip Ruddock worked together to change the Marriage Act of Australia. The purpose of those changes was to prevent an interpretation of the Marriage Act that would have allowed person of the same gender to get married. They argued that this was simply to clarify and maintain the status quo. The reality of the change was that it flew in the face of our obligations under the Hague Convention which is about respecting those relationships which have been registered in differing jurisdictions. These changes were made in the parliament, by the parliament, with no reference to the electors.
Of course there has been significant changes in the understanding of marriage in society have happened in the intervening years, and there are now a growing number of jurisdictions in the world where single gender marriages are legal, accepted and performed. This is seen as a matter of social justice and general indications are that more than two-thirds of the Australian electorate is in favour of the matter proceeding.
It is now a matter of the ALP Platform, and it has been a key plank in the Greens platform for quite a few years. The LNP have been rather more nuanced on the subject no doubt in part because the last PM was dead against it. The split in the coalition is largely the conservative/liberal split that affects much of their policy making. At some stage they resolved, as a deferral technique to have a plebiscite on the subject. Now they are in government, and both the Greens and the ALP say they will not support a plebiscite.
The truth is that the politics of this has become tedious. Clearly the right approach now is to allow the parliament to vote on the matter, and sure, have it as a non-party conscience vote, and take it from there. 99% of Australians believe we are going to have Marriage Equality Legislation, and most of us believe we should. Lets just save the couple of hundred million a plebiscite will cost and just do it. Good budget repair mechanism and take the politics out of the matter.