(CNN) — The U.S. Supreme Court takes up the first of two cases about same sex marriage today (Tuesday) with the justices listening to oral arguments on California's ban on gay marriage.
Same sex couple's from California are challenging the state's Proposition 8 that was passed in 2008. It bans same sex marriage. California voters approved the ban.
Challengers argue the 14th amendment guarantees "equal protection" so defining marriage as only between a man and a woman violates their equal rights.
Experts says it'll be hard for the court to ignore a huge shift in public opinion. 20 years ago most of the country opposed same-sex marriage, now more and more Americans are changing their minds.
According to a CNN/OCR poll done just last weekend, the majority of Americans now support gay marriage and more politicians are shifting their stance too.
9 states plus Washington DC allow same sex marriage, but 38 states do not.