Yu said the court's explanation means that even if lawmakers do not pass legislation allowing same-sex marriage in the next two years, gay couples will still be able to marry by this time in 2019.

"I hope that the legislators will have the moral courage to pass same-sex marriage into law, however it is hard to predict how long it will take, at this moment," she said. "The opposition toward gay marriage in Taiwan won't just gladly accept it and give up the debate, so the debate will continue."

Draft legislation is already making its way through Taiwan's Parliament but it has stalled.

"We feel that this is a huge success for the LGBT and marriage equality movement in Taiwan," said Wayne Lin, an activist who runs an LGBT hotline on the island.

"We want to amend the Civil Code so same-sex couples can get married... our target is to complete this whole process within this year."

Tsai Ing-wen, Taiwan's first female president, expressed support for gay marriage before her election in 2016.

"In the face of love, everyone is equal," she said in a Facebook video during 2015's gay pride parade.

"I support marriage equality. Every person should be able to look for love freely, and freely seek their own happiness."

The decision came in response to two requests for a Constitutional Court ruling on article 972 of Taiwan's civil code, which states that marriage is between a man and a woman.

One of the requests was filed in 2015 by Chi Chia-wei, a veteran gay rights activist who has spent more than half his life fighting for marriage equality in Taiwan, according to the island's official Central News Agency (CNA).

Japan does not recognize same-sex marriage, although a handful of cities and wards have legalized same-sex partnerships. However, LGBT people are not protected from discrimination under Japanese law.

Homosexuality is not illegal in China and the Communist government removed it from the official list of mental disorders 16 years ago, but activists and experts say that prejudice and discrimination persist.