Imagine that a gay man made a move on a friend, who was so offended by the sexual connotation that he killed the gay man in a fit of rage. Instead of being charged with murder, the charge was downgraded to manslaughter, since the unwanted homosexual advance apparently provoked the friend to murder. This is no hypothetical, it's a legal argument known as the homosexual advance defence and it was used in Queensland just last year. The case involved a man who was beaten to death by two acquaintances after he apparently made sexual advances to one of them. The homosexual advance defence also remains admissible in law in NSW. Debate erupted again over the issue in Queensland following an op-ed in the Brisbane Times last week, where Alan Berman declared Queensland's legal system as "outmoded and retrograde" for allowing the defence. Queensland Deputy Premier and Attorney-General Paul Lucas responded, explaining that a bill passed last month closed many of the loopholes used in the provocation defence, but it didn't change the "non-violent sexual advance" (the specific legal term used by those arguing the homosexual advance defence) as it protected women suffering domestic violence who were provoked into killing their attackers and each individual case needed to be examined by a judge. "That an unwanted gay sexual advance can be considered sufficient provocation for a brutal and sustained attack is a disturbing example of entrenched social biases favouring straight men," wrote David Donaldson in an essay exploring the homosexual advance defence in the latest issue of Overland. When discussing gay marriage on ABC's Q&A last year PM Julia Gillard said: "As a government, we have said there are all sorts of discriminations that have been in place against same-sex couples that we've wanted to fix and take away. And so we've gone through federal legislation and worked to take those discriminations away." It wasn't the first or the last time that Gillard noted how -- apart from gay marriage -- the government worked to remove all legal discriminations against same-sex couples. Yet the homosexual advance defence remains. What other laws -- criminal and otherwise -- still discriminate specifically against non-heterosexual Australians? It's a long list, complicated by a myriad of state-based legislation and differences amongst the states on what laws apply where and to whom. Marriage: It's the most obvious and publicly debated form of discrimination against same-s-x couples in Australia: the Marriage Act specifes that "marriage means the union of a man and a woman". The Howard government introduced this definition in 2004 after various other Commonwealth countries introduced same-s-x marriage. But as ACT Chief Minister John Stanhope pointed out recently, Howard may have accidentally opened up the path for states to legalise same-s-x marriage in his attempt to squash it federally. Laws of consent: Although the age of sexual consent varies from 16 to 17 in most Australian states, Queensland remains the only state to still have a different age of consent for anal s-x. Young Queenslanders must be 18 years old to engage in anal sex, while 16-year-olds can have vaginal sex, a difference that Senior Law Lecturer at ANU, Wayne Morgan, calls "indirect discrimination" against young gay men. Queensland's unlawful sodomy law carries a maximum penalty of 14 years jail. Laws regarding parenting: A myriad of issues occur around same-sex parenting, particularly because of different state laws regarding surrogacy, adoption and assisted reproduction technology (ART). Same-sex couples can now adopt in NSW, Western Australia, the ACT and to a limited extent in Tasmania. It remains illegal for gay couples to adopt children they are not biologically related to in Victoria, Queensland, South Australia and the Northern Territory, however in Victoria and Queensland (and in special circumstances in the NT) a gay person can adopt a child, just not a couple. (Not that it's only gay couples struggling with these laws; the NT bans de facto straight couples from adopting). This can mean while one parent is legally recognised, the co-parent may not have the same legal protection of their children. In January, a gay couple in Melbourne were awarded full parenting rights to their child conceived via surrogacy with a mother overseas. NSW, Victoria and Queensland allow birth rights to a baby born via surrogacy to same-s-x parents. Tasmania is currently debating a new bill over surrogacy, with calls from the Tasmanian Liberal Party to leave same-sex parents off the bill, which would effectively criminalise surrogacy for same-sex parents. ACT, Tasmania and Western Australia are the only states that allow full parenting rights to same-sex couples whose children are born through ART. With lesbian couples, it is often only the birth mother who has official legal parental status, with only the ACT allowing lesbian partners to share full parenting rights, although WA and NT do allow a "presumption of parentage" for the co-mother. Rodney Croome, campaign director of Australian Marriage Equality, says these laws can have practical problems, such as co-parents being unable to sign permission slips for their children at school or in an emergency medical situation where forms need to be signed at a hospital. If gay marriage was legalised, many of these discrepancies in parenting laws would disappear, and vice-versa, says Croome. Offensive behaviour laws: While nearly all criminal laws no longer obviously discriminate against gay people, the enforcement of "offensive behaviour" laws by police often discriminate against the gay community. Offensive behaviour laws cover having sex in a public area, and are regularly used to prosecute gay men having sex at "beats", while it's more common, says Morgan, for straight couples caught mid-tryst in public to just get told to move on. "It is still enforced in a discriminatory manner against gay men," he said, "though it looks inoffensive on the books." Anti-discrimation laws: Anti-discrimination laws vary state to state, with no national law protecting against discrimination based on sexuality or gender. There is particularly few protections for those who are intersex or transgender. Both NSW and Western Australia allow exemptions to their anti-discrimination laws for religious groups, meaning Catholic schools can refuse to hire a lesbian teacher, religious organisations can discriminate against gay job applicants, etc. And while not a law, gay men in Australia (or any male who has had male-to-male sex in the last year) are still forbidden to donate blood for fear of HIV transmission. This is regardless of a gay man's s-xual history or relationship status. So it's not just gay marriage holding back equality for Australia's LGBT communities. "We can't say that same-sex attracted people are treated equally in laws by government," said Croome. "Yes, in some issues, in some states, but not all issues, in all states."