AHANDFUL of gay activists gathered in the public gallery of Tasmania's colonial sandstone Parliament House recently, and in celebration threw down upon the politicians below rolls of paper streamers. It was a cheeky, small town scene. Hardly equal to the international reverberation in the politics of sex that the Tasmanian Gay and Lesbian Rights Group believes it has just achieved. Their victory came when the United Nations Human Rights Committee (UNHRC) in a decision handed down from Geneva determined Tasmania's state law criminalising homosexual sex amounted to discrimination, and should be repealed. As a result of this decision the tiny Tasmanian Gay and Lesbian Rights Group claims a global victory against any discrimination by reason of a person's sexual orientation. In backing the decriminalisation of homosexuality in the state, the UN committee has also stated, for what legal experts say is the first time, that human rights apply to all people, regardless of their sexual orientation. Gay activist Mr Rodney Croome, who is the driving force behind the case fought in the name of his partner Mr Nick Toonen, said jubilantly: ''it has been decided once and for all that gay and lesbian rights are human rights''. In the first Australian case to be brought before the committee, Mr Toonen claimed that sections of the Tasmanian Criminal Code prohibiting homosexual sex as ''crimes against the order of nature'' violate articles of the UN's International Covenant on Civil and Political Rights (ICCPR). As well as agreeing and ordering their repeal, the UNHRC also said that articles Two and 26 of the ICCPR which prohibited discrimination on the grounds of sex, race, religion or other status in fact also covered sexual orientation. ''In (the committee's) view the reference to 'sex'. . . is to be taken to include sexual orientation.'' A Melbourne University law lecturer who has been adviser to the Tasmanian gays, Mr Wayne Morgan, said the finding on sexual orientation made it likely that other cases of discrimination on similar grounds from other countries would succeed. ''The ICCPR is the major human rights treaty of the UN system with 114 countries party to it,'' he said. ''This is certainly the first time the committee has looked at this issue (of sexual orientation). This is an extremely important and useful decision for gay men and lesbians throughout the world.'' It is increasingly apparent that Tasmania is standing out against the rest of Australia. Among the organisations calling for a change to its laws are the Australian Medical Association, the Liberal Party's own national Young Liberals organisation, the Anglican and Uniting Churches. Now that the UN decision has been handed down, the Federal Government in Canberra as party to the ICCPR has been asked to respond by mid-July. The Federal Attorney-General, Michael Lavarch, is to begin negotiations with the state next month, and the state's Attorney-General Ron Cornish has declared a readiness to argue Tasmania's case before him. At their demonstrations at the state parliament last week, speakers were emphatically confident: Tasmania's laws will be repealed.