性悖軌法（英語：Sodomy law）是一种把特定性行为定位為性犯罪的法律。此类性行为通常指肛交，有时其定义会被扩大到不能生殖的性行為，如自慰、口交等等[1][2][3]。根据威廉·布莱克斯通的《英国法释义》，性悖軌法被限定为“違抗自然法的可惡罪行”（abominable and detestable crime against nature）或一些类似的描述性用词。这种模糊不清的用語定义，使各種特定行为都能以這種名目納入懲處範圍之中。一些中世紀基督教神學家把男上女下位以外的性交姿勢，基督徒和異教徒（猶太人、穆斯林）的性交行為，都視為違反自然法的性行為（Sodomy）[4]。
“sin of Sodom”來自於《圣经》创世纪第18、19章中耶和華和亞伯拉罕的故事。耶和華认为所多瑪與蛾摩拉（Sodom and Gomorrah，是古代巴勒斯坦的城市）被道德败坏且罪恶深重的人群占据，所以，耶和華告诉亚伯拉罕他要毁掉这两个城市。亚伯拉罕替居住在两个城市的人求情，最后耶和華同意，如果能在城市里找到10个清白的人，他就宽恕整个城市。于是，耶和華派了两个天使去考察所多玛，他们受到所多玛最后一个清白的人、亞伯拉罕的小舅羅得的热情款待。可是在天使要睡觉的时候，所多玛的居民围住了羅得的房子，要求和羅得的“客人”发生性关系。
在南澳州废除性悖轨法之后，澳洲首都特区于1976年、维多利亚州于1981年以及诺福克岛于1993年都废除了性悖轨法。与南澳州一样，这些州在废除性悖轨法的同时，也都给予了任意性别人士之间的肛交以和其他性行为平等的法律规定（包括同意年龄、反强奸等等）。[來源請求]西澳洲于1989年通过了1989年法律改革（肛交去罪化）法案废除了性悖轨法。新南威尔士州与北领地也在1984年进行了类似的修法对肛交进行了去罪化。然而，在修法之时，这些州对于肛交的同意年龄是不与其他性行为平等的。新南威尔士州和北领地将同意年龄定位18岁，而西澳洲将同意年龄定位了21岁。之后，从1997年开始，这些州开始倾向修改法律使同意年龄变得平等。西澳洲于2002年修改了这样的法律，而新南威尔士和北领地则在2003年修改了这样的法律。而塔斯马尼亚则在1997年图能诉澳大利亚案（英语：Toonen v Australia）和特鲁姆诉塔斯马尼亚案之后成为了最后一个废除性悖轨法的澳洲司法辖区（然而，值得注意的是，塔斯马尼亚在2004年2003关系法案生效之后成为了第一个承认同性伴侣关系的澳洲司法辖区）。[14]在2016年，昆士兰也终于修改法律，将肛交的同意年龄从18岁降低至平等的16岁，成为了澳洲最后一个将同意年龄平等化的司法辖区。[15]
在《马来西亚刑事法典》（英語：Laws of Malaysia - Penal Code）第377条文里，肛交被认为是悖軌的性行为，任何肛交的行为均属违法。一旦肛交罪成立，罪犯可被判处有期徒刑五年至二十年，并可處鞭刑。知名的官員安華，就因被指控此罪而多次入獄，雖然安華堅持否認此項指控，並堅稱自己是異性戀者。
然而，美军的情况有所不同。由于“军队是一个在需要的时候与平民完全隔离的社会”[31]，美军的性悖轨法依然有效。统一军法典第125条并未因劳伦斯诉德克萨斯州案被完全废除。美国军事上诉法庭承认劳伦斯诉德克萨斯州一案适用于军法第125条。然而，在美国诉史提华和美国诉马尔科母（英语：United States v. Marcum）一案中，法院虽然判决“（该被告人的）行为符合最高法院所规定的自由利益”[32]，却继续说明虽然劳伦斯案可以适用于军法系统，125条仍然可以在“军队独特的情况”下在任何劳伦斯案所保护的自由外适用。[33]这些自由的例子有：为军队所禁止的等级之间的过分亲密、公开性行为、或者任何有可能影响正常秩序和纪律的行为。[33]在劳伦斯案之后，仍有如美国诉米诺[來源請求]和美国诉布拉克[34]等双方同意的肛交仍被定罪的情况。
^Andrew Sullivan. Unnatural Law. The New Republic. 2003 [2017-05-04]. （原始内容存档于2021-03-06）. It's worth noting, then, that from the very beginning sodomy and homosexuality were two categorically separate things. The correct definition of sodomy--then and now--is simply non-procreative sex, whether practiced by heterosexuals or homosexuals. It includes oral sex, masturbation, mutual masturbation, contraceptive sex, coitus interruptus, and anal sex--any sex in which semen does not find its way into a uterus. So it's perhaps unsurprising that Jordan's research doesn't discover the actual nouns "sodomy" and "sodomite" until the eleventh century. The first and most influential polemic against it was the hermit monk Peter Damian's Book of Gomorrah. Given the period's expansive definition of sodomy (it did, after all, include masturbation), it's not surprising that Damian believed it was rife. But his particular fixation--which has persisted in religious teachings ever since--is with same-sex male sodomy.
^Quibian Salazar-Moreno. Weird sex laws in the U.S.. [2018-11-09]. （原始内容存档于2021-10-09）. Up until 1962, sodomy was considered a felony and, in some states, oral sex, adultery and masturbation fell under the sodomy laws.
^Francis Mark Mondimore. A Natural History of Homosexuality. 1996 [2017-05-04]. （原始内容存档于2021-03-06）. According to some medieval writers, heterosexual intercourse in other than male-superior position was an act of sodomy because the chances of conception were thought to be lessened...Not all medieval theologians relied on the litmus test of procreative potential to classify sexual sins, however. Many regarded sex between Christians and Jews or between Christians and Muslims as sodomy-even potentially procreative sexual acts could be forbidden if improper partners were involved.
^Sullivan, Andrew. Unnatural Law. The New Republic. March 24, 2003 [November 27, 2009]. （原始内容存档于2010-07-02）. Since the laws had rarely been enforced against heterosexuals, there was no sense of urgency about their repeal. (Or Sullivan, Andrew. Unnatural Law. The New Republic. 2003-03-24, 228 (11).)
^Andrew Sullivan. Unnatural Law. The New Republic. 2003 [2019-09-15]. （原始内容存档于2021-03-06）. It's worth noting, then, that from the very beginning sodomy and homosexuality were two categorically separate things. The correct definition of sodomy--then and now--is simply non-procreative sex, whether practiced by heterosexuals or homosexuals. It includes oral sex, masturbation, mutual masturbation, contraceptive sex, coitus interruptus, and anal sex--any sex in which semen does not find its way into a uterus. So it's perhaps unsurprising that Jordan's research doesn't discover the actual nouns "sodomy" and "sodomite" until the eleventh century. The first and most influential polemic against it was the hermit monk Peter Damian's Book of Gomorrah. Given the period's expansive definition of sodomy (it did, after all, include masturbation), it's not surprising that Damian believed it was rife. But his particular fixation--which has persisted in religious teachings ever since--is with same-sex male sodomy.
^Quibian Salazar-Moreno. Weird sex laws in the U.S.. [2019-09-15]. （原始内容存档于2021-10-09）. Up until 1962, sodomy was considered a felony and, in some states, oral sex, adultery and masturbation fell under the sodomy laws.
^ 12.012.1Andrew Sullivan. Unnatural Law. The New Republic. 2003 [2019-09-15]. （原始内容存档于2021-03-06）. It's worth noting, then, that from the very beginning sodomy and homosexuality were two categorically separate things. The correct definition of sodomy--then and now--is simply non-procreative sex, whether practiced by heterosexuals or homosexuals. It includes oral sex, masturbation, mutual masturbation, contraceptive sex, coitus interruptus, and anal sex--any sex in which semen does not find its way into a uterus. So it's perhaps unsurprising that Jordan's research doesn't discover the actual nouns "sodomy" and "sodomite" until the eleventh century. The first and most influential polemic against it was the hermit monk Peter Damian's Book of Gomorrah. Given the period's expansive definition of sodomy (it did, after all, include masturbation), it's not surprising that Damian believed it was rife. But his particular fixation--which has persisted in religious teachings ever since--is with same-sex male sodomy.
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