A ruling by Japan’s Supreme Court last month could lead to same-sex couples being able to marry.

The ruling was made in a lawsuit filed by married opposite-sex couples objecting to the requirement under the Civil Code that they register under only one surname.

The majority of the 15-strong Supreme Court panel ruled that the plaintiffs’ rights were not being violated by the Civil Code.

However Sota Kimura, an associate professor at the Tokyo Metropolitan University noted the wording used by the judges in their decision.

Kimura pointed to the fact that it is the first time the judges have ruled on Article 24, which defines marriage as a legally binding union between two people.

Some translations suggest that marriage only applies to opposite-sex couples, however the word “ryōsei” can also mean simply “two parties”.

Kimura said he thinks the Supreme Court judges were stressing the latter interpretation of the word.

He said because the judges did not explicitly limit the definition of marriage to one man and one woman, this could open the door to same-sex marriage becoming legal in Japan.

Kimura says that if a couple eventually a same-sex couple sued the state to have their marriage recognised, this latest ruling could be used as a precedent.

However the Japanese Prime Minister Shinzo Abe has said the Constitution would need to be revised before same-sex marriage rights could be allowed.