At the Congressional Human Rights Caucus in 1987 in Washington, D.C., the Dalai Lama gave a speech outlining his ideas for the future status of Tibet. The plan called for Tibet to become a democratic "zone of peace" without nuclear weapons, and with support for human rights, that barred the entry of Han Chinese. The plan would come to be known as the "Strasbourg proposal", because the Dalai Lama expanded on the plan at Strasbourg on 15 June 1988. There, he proposed the creation of a self-governing Tibet "in association with the People's Republic of China." This would have been pursued by negotiations with the PRC government, but the plan was rejected by the Tibetan Government-in-Exile in 1991. The Dalai Lama has indicated that he wishes to return to Tibet only if the People's Republic of China agrees not to make any precondition for his return. In the 1970s, the then-Paramount leader Deng Xiaoping set China's sole return requirement to the Dalai Lama as that he "must [come back] as a Chinese citizen... that is, patriotism".  The Dalai Lama celebrated his seventieth birthday on 6 July 2005. About 10,000 Tibetan refugees, monks and foreign tourists gathered outside his home. Patriarch Alexius II of the Russian Orthodox Church alleged positive relations with Buddhists. However, later that year, the Russian state prevented the Dalai Lama from fulfilling an invitation to the traditionally Buddhist republic of Kalmykia. Then President of the Republic of China (Taiwan), Chen Shui-bian, attended an evening celebrating the Dalai Lama's birthday at the Chiang Kai-shek Memorial Hall in Taipei. In October 2008 in Japan, the Dalai Lama addressed the 2008 Tibetan violence that had erupted and that the Chinese government accused him of fomenting. He responded that he had "lost faith" in efforts to negotiate with the Chinese government, and that it was "up to the Tibetan people" to decide what to do.  30 Taiwanese aborigines protested against the Dalai Lama during his visit to Taiwan after Typhoon Morakot and denounced it as politically motivated.  The Dalai Lama is an advocate for a world free of nuclear weapons, and currently serves on the Advisory Council of the Nuclear Age Peace Foundation.  The Dalai Lama has voiced his support for the Campaign for the Establishment of a United Nations Parliamentary Assembly, an organisation which campaigns for democratic reformation of the United Nations, and the creation of a more accountable international political system.

Answer this question "What issue did he advocate for?" by extracting the answer from the text above.
The Dalai Lama is an advocate for a world free of nuclear weapons,