Hundreds of members of the gay, lesbian, bisexual and transgender community filed an unprecedented request Tuesday with the Japan Federation of Bar Associations (JFBA) in a bid to legalize same-sex marriages, saying Japan’s failure to recognize the practice constitutes a violation of human rights.

Coming on the heels of what lawyers behind the move called a gradual softening of traditional prejudice toward gays in Japan, the bid by 455 individuals is the first attempt to legalize same-sex marriages by appealing over human rights.

The JFBA, the nation’s biggest bar association, will investigate the allegation and, if necessary, issue a warning to the central government to review its approach toward the matter.

Although legally nonbinding, a warning would have a “far-reaching” impact on the nation’s legislative and judicial process, said Toshimasa Yamashita, one of the lawyers involved.

“If issued, the warning will be quite comprehensive, formulated based on the bar association’s meticulous research and analysis,” Yamashita told a news conference Tuesday in Tokyo. “It will likely be used as a reference in Diet sessions or trials whenever the topic of same-sex marriages arises.”

The lawyer added that he believes the landmark ruling handed down by the U.S. Supreme Court last month that declared same-sex marriages legal nationwide will provide momentum to the case.

The request states that Japan’s failure to acknowledge same-sex marriage is unconstitutional in that it contradicts the principle of equality and individual dignity as guaranteed by the Constitution. Although Japan does not outlaw same-sex marriages as some countries do, its lack of a system to grant same-sex unions the status of matrimony exposes couples to “a wide variety of disadvantages” in life, thus robbing them of the “right to pursue happiness” as stipulated by the Constitution, the petitioners argue.

Such disadvantages include not being allowed to designate their partners as inheritance beneficiaries in the event that they die without a will or to make accessible to them a batch of health insurance benefits usually granted to spouses.

In instances where one partner is non-Japanese, the foreigner is not eligible to hold a spouse visa — unlike a heterosexual counterpart.

One of the petitioners who spoke at a news conference Tuesday was a Tokyo resident in her 40s who only wished to be identified as Kei.

She said she was ashamed to recall how her mother was hospitalized in critical condition one day and, when Kei could not get there, her long-term partner rushed to the hospital instead. But staff refused to disclose anything about Kei’s mother’s condition because under the eyes of the law they were strangers.

“I spent more than half of my life being unable to tell anything about my partner even to my parents and friends. I could only hope the children of current and future generations don’t have to live the kind of life I did and can be celebrated regardless of whether they like people of the opposite sex or not,” Kei said.