I read it from a Taiwanese commentary

對此，陸委會來函解釋，依據兩岸人民關係條例，兩岸婚姻須先在中國結婚才能來台登記。但中國目前不承認同性婚姻，因此上述條件根本無法成立。陸委會也同時說明，兩岸婚姻須遵守現行規定，避免危害到國家安全及社會安定。

Generally speaking, the law for cross-strait marriage (between a mainland Chinese and a Taiwanese, regardless of same sex marriage or not) requires that the couple to wed in mainland China first, and only then can they register in Taiwan. Because PRC currently does not recognize same sex marriage, such arrangement is not possible at the moment.

I’m not sure how well the machine translation works but do give the article a read, it’s a short commentary about the future of LGBT legalization in Taiwan.