This week the Senate will effectively decide whether or not Australians will go to the polls early next year to vote on whether or not LGBTI couples are extended the same right to marriage as heterosexual couples. But why does the question of whether or not to hold a plebiscite have to go before the Parliament?

Opposition Leader Bill Shorten is giving strong signals that the Labor leadership is inclined to oppose the plebiscite legislation. Crikey understands that if the matter comes before Labor caucus today, it is likely that there will be a unity ticket between the Left and the Right in Labor against it. The Left oppose the matter on the grounds they’ve made known publicly — that the debate will bring out hate speech from anti-gay groups and hurt the LGBTI community. The Right oppose it as a means to wedge Prime Minister Malcolm Turnbull and pressure him to stand up to the conservatives in his party.

If Labor ultimately opposes it, the government will be reliant on the votes of Nick Xenophon and co in order to pass the legislation through the Senate. Xenophon said today that still couldn’t see the point of the plebiscite and indicated he would oppose it.

Ultimately, the government can hold a plebiscite whenever it wants without needing to pass legislation, but there are a number of factors built into the marriage plebiscite that would require legislation.

The rules

While the rules around a referendum are defined in law now, there is nothing in law to say exactly how a plebiscite will be run. Paul Kildea, a senior law lecturer at the University of New South Wales, told Crikey that legislation would need to set out when the plebiscite will be held, how the results will be announced, and what counts as a formal vote, such as whether a tick or a cross means a certain thing for either a yes or no vote. Kildea said that the government would likely attempt to model the legislation closely on referendum legislation.

[Essential: No to plebiscite case funding — and no to foreign investment]

“As much as possible, the government may wish to have the plebiscite act just adopt relevant provisions of the referendum act and that’s probably a simple way of doing it. And then just alter those provisions as is necessary for the plebiscite,” he said.

One potential change, however, would be to change the threshold for the outcome. Whereas in a referendum it is a majority of votes in a majority of states, Prime Minister Malcolm Turnbull has indicated it would be a simple majority, although results would still be broken down, electorate by electorate — something conservative MPs will likely use to continue to vote against marriage equality in Parliament.

The question

The much-debated wording of the question will also likely need to be set out in the legislation. The leak to the Sunday Telegraph this month suggests the working question is:

“Do you approve of a law to permit people of the same sex to marry?”

The wording of this question is already controversial among pro-marriage equality campaigners, and those opposed, as the government had not widely consulted on the proposed question. Government ministers said after the report that the final wording of the question had yet to be decided.

Compulsory vote

In order to get every voting Australian to at least turn up to a polling booth like they do at the election, the government will need to include in the legislation making it compulsory. Unfortunately, this compulsory vote doesn’t extend to the Parliament, and legislation cannot bind MPs to vote for marriage equality if the plebiscite votes in favour of it.

“There’s no way to bind MPs to voting a particular way,” Kildea said, adding that the only way it would be possible would be to pass the change to the Marriage Act with the plebiscite legislation with a provision that the change would only come into effect if the majority of Australians voted yes.

“That’s the closest you can get to having the plebiscite binding. It attaches consequences to the vote.”

The funding

Even if the government can secure enough votes in Parliament to support the establishment of the plebiscite — and it is still looking somewhat unlikely at this stage — there is a significant pushback from the yes side against government funding being allocated to either campaign. In the somewhat less contentious 1977 plebiscite to change the national anthem, the government allocated $94,000 in the last week before the vote for radio, TV and print ads about each of the four proposed national songs for Australians to vote on. These were government ads, and it predated the High Court rulings in 2014 establishing the need to pass legislation in order for the government to spend money in certain ways.

The two successful High Court cases in 2014 challenging the federal government’s funding for the school chaplaincy program established that, in order to spend money, the government in most cases needed legislative authorisation.

[How Coalition homophobes could set marriage plebiscite up to fail]

“It’s understood most of the time to spend money, the government will require legislation that is connected to a head of legislative power in the constitution,” Kildea said.

This means that the legislation will need to set out the intention to provide funding to the yes and no sides, Kildea says.

The form of the question and the issue of funding are the most likely points of amendment once the legislation hits Parliament. A recent Essential poll stated that while 62% of the population are in favour of same-sex marriage, 62% of the population also oppose public funding for the yes and no sides.

Australian Marriage Equality — the lobby group likely to lead the yes side in the event of a plebiscite — is not in favour of public funding, but the Australian Christian Lobby — one of the major voices on the no side — wants equal funding and a ban on overseas funding during the plebiscite. Although that might mean the government would need to assess the problem of foreign donations in politics generally.