Marriage bans for same-sex couples in Wisconsin and Indiana are under review Tuesday by the 7th Circuit Court of Appeals, the fourth such court to hold hearings on same-sex marriage bans this year, MSNBC reported.

But it will be the fifth hearing since the Defense of Marriage Act (DOMA) ruling last year which cleared the way for legalization of same-sex marriages nation-wide.

Same-sex unions are legal in 19 states and the District of Columbia, Bloomberg reported.

Eleven other court decisions to overturn bans are on hold for appeals.

Andrew Koppelman, a professor at Northwestern University's law school in Chicago, told Bloomberg that while it may lead to more success for pro-equality advocates, there are no guarantees.

The court received several briefs that support ruling the ban unconstitutional.

The historically black Howard University School of Law compared the bans on same-sex marriages are similar to what interracial couples faced in the past, according to the Lafayette Journal & Courier.

"Today, while there is no longer any serious claim that marriage rights should be denied on the basis of race, opponents of marriage equality have attacked same-sex couples, using precisely the same flawed arguments that once were used to justify racial slavery and apartheid," HU wrote in the brief, according to the Journal & Courier.

Businesses weighed in on the issue as well.

"States like Wisconsin and Indiana, whose laws or constitutions prohibit same-sex couples from marrying, require us to differentiate among similarly situated employees to our detriment. As a result, our ability to grow and maintain a diverse workplace is hampered, as is our ability to grow and maintain our business," Indiana-based Cummins and WellPoint said, according to the Journal & Courier.

"The more victories the proponents of same-sex marriage pile up in the lower courts, the better off they'll be in the Supreme Court. It'll be a big step for the Supreme Court to legalize same-sex marriage throughout the United States. The more lower courts agree with them, the more confident they will be about doing that," Koppelman told Bloomberg.