As same-sex couples in the state of North Dakota on Friday filed a lawsuit challenging the state’s same-sex marriage ban, there are now no states with unchallenged bans.

Until Friday, North Dakota was the only state in the US which had an unchallenged ban on gay and lesbian couples marrying, but that all changed as seven couples filed a lawsuit challenging it.

Same-sex marriage is currently recognised in 20 states and the District of Columbia, and following the announcement North Dakota’s lawsuit, all of the remaining 31 are now facing legal challenges.

Minneapolis attorney Josh Newville filed the lawsuit in North Dakota on behalf of the seven couples. He recently challenged South Dakota’s ban on behalf of six couples.

Five gay and lesbian couples in the US state of Alaska filed a lawsuit two weeks ago, challenging the state’s ban on same-sex marriage, leaving only three states with unchallenged bans.

Then, that Wednesday, four couples in the state of Montana filed a lawsuit challenging the state’s ban.

Following a filing by a lesbian couple in South Dakota the number dropped to just one.

Proponents of same-sex marriage have had an extensive winning streak in courts across the US, following the Supreme Court’s decision to strike down the Defence of Marriage Act (DOMA) last year.

Since that case, not a single ruling has found against the right of same-sex couples to marry, urging litigation in more and more states.

Last month, judges in Oregon and Pennsylvania found in favour of same-sex couples, allowing them to marry.

US District Judge John Jones wrote in the Pennsylvania ruling: “We are a better people than what these laws represent, and it is time to discard them into the ash heap of history.”