Get Up's marriage equality ad has been viewed more than 16 million times online. Credit:Get Up Ads cannot vilify or discriminate against people based on their sexual preference (or race, gender and other factors). Misleading or deceptive messages are also prohibited. Political ads, however, are exempt from all of these limitations. This suits the ASB and the Australian Communications and Media Authority just fine. Neither wants control over party-political ads, lest they be seen as biased – or hampering free speech. And the Australian Electoral Commission will only take action if an ad encourages ballot papers to be wrongly marked. So what defines a "political" ad? Obviously, any commercial urging you to vote (or not vote) for a specific party is political. In an election, networks must give all existing parties a "reasonable opportunity" to buy advertising space – but not equal time. Lobby groups don't enjoy the same right. Networks are free to reject their ads, even outside an election period. In 2012, for instance, commercial channels banned an ad criticising Woolworths and Coles for their poker machine interests. In 2015, the Seven and Ten networks refused an anti-marriage equality ad, while Nine and Foxtel aired it.

An ad from the Marriage Alliance shows same-sex marriage as an iceberg with the tagline, "It's not as simple as you think". Credit:Marriage Alliance Yet ACMA, the broadcasting watchdog, views most lobby group ads as "political". Therefore, they must be tagged with certain details, including the name of the authorising party. (In March, ACMA found Ten had breached its rules by airing an anti-abortion ad with no authorisation tag. Later that month, Foxtel was caught screening a pro-marriage equality message without a tag.) Fairfax Media understands all same-sex marriage ads will be classed as "political", meaning they are not bound by standard discrimination and vilification rules. Educational ads alerting people to the postal vote are only exception. Same-sex marriage enjoys support in the community but the Coalition has struggled to deal with the issue internally. Credit:SMH With this vote set to open in a few weeks, all three commercial networks – plus SBS and Foxtel – are committing to air ads from the "yes" and "no" camps. Yet each retains its right to decline them as they see fit.

Consider SBS, which requires all ads meet its editorial guidelines. This allows the network to reject those that conflict with its code of practice – including its mission to "counter attitudes of prejudice against any person or group on the basis of their ... sexual preference". A man proposes to his partner in Get Up's 2011 marriage equality ad. Credit:Get Up When a commercial is deemed 'political', it is no longer bound by standard discrimination and vilification rules. A commercial TV executive says: "It'll be interesting to see if Channel Ten allows anti-equality messages to clog up The Project's ad breaks ... that could anger their audience and spark a boycott." Already, major advertising agencies have promised to refuse work from the "no" side. When the Turnbull government proposed a mandatory plebiscite, it wanted to extend the "reasonable opportunity" law to the "yes" and "no" camps. Now that it's pursuing a postal vote – High Court challenge notwithstanding – it is considering new rules for public debate. Acting Special Minister of State, Senator Mathias Cormann, declined to specify these rules. Fairfax Media understands a bill has been drafted, and is being scrutinised by Labor and the Greens. Neither party will comment until they have finalised their positions.

The fate of same-sex marriage could be determined by a postal plebiscite. Credit:Phil Carrick At this point, other problems emerge. If the "reasonable opportunity" rule is enforced before the postal vote, it could embolden other lobby groups to demand the same right in future. "TV stations couldn't outright refuse to run an ad – and most political ads aren't subject to misleading advertising laws," equality advocates Hannah Marshall and Michael Bradley, from Marque Lawyers, said in a statement. "That's a terrible combination ... the coal lobby could force [the broadcast] of ads claiming that global warming's a myth." Fiona Jolly, CEO of the ASB, says, "Our view is that any advertising should respect [current] standards, regardless of whether it's political or not." To give the "yes" and "no" lobbies a "reasonable opportunity" to buy ads, the Parliament must amend the Broadcasting Services Act 1992. This shouldn't undermine the government in its High Court battle, says constitutional law expert George Williams – as long as the change is temporary, and limited to the postal survey. The bigger issue, he believes, is the government's questionable assertion it can hold a postal vote without parliamentary support.

If someone believes they've been defamed by a same-sex marriage ad, they can seek redress under statutory or common law. Except this rarely occurs with political ads, because of the cost and time involved. What's more, attempts to introduce restrictions could backfire. "If [the government] limits the harmful things that can be said about gay people," says one Labor figure, "why wouldn't women and religious minorities demand equal protections down the track? Not to mention the backlash they'll cop from the 18c nuts [conservatives opposed to the "offend and insult" provisions of the Racial Discrimination Act]. Loading "And if the networks turn down ads from the "no" side, the government can't complain if this affects the result. We've said all along that a postal vote is flawed." Political marketing expert Andrew Hughes, from the Australian National University, believe attack ads have lost their potency. "There's increasing concern it's turning people off democracy," he says. "People switch off. Their attitude is, 'Why can't you talk about what you're offering? Don't tell me why the other side is so terrible'."