Is same-sex marriage a constitutional right?

CHICAGO (WLS) -- Is same-sex marriage a constitutional right? As the U.S. Supreme Court heard arguments in a landmark case that could legalize gay marriage in every state, gay marriage supporters rallied in Chicago.

Before the nine justices are two questions: Does a state have a constitutional obligation to perform a marriage? And is a state obligated to recognize a marriage from another state?

"If I'm married on Illinois and I go to Ohio, Is Ohio constitutionally obligated to recognize my marriage?" Jim Bennett, Midwest Executive Director of Lambda Legal, said.

Representing many gay marriage cases on the state level, Lambda Legal listened to Tuesday's arguments for any signs from Chief Justice John Roberts and Justice Anthony Kennedy, both of whom are viewed as the deciding votes.

"You say join in in the institution. The argument on the other side is that they're seeking to redefine the institution," Chief Justice Roberts said.

"This definition has been with us for millennia and it's very difficult for the court to say, oh well, we know better," Justice Kennedy said.

Kennedy and Roberts made comments and asked questions of both sides, which made it difficult to read how they may vote. Bennett hopes Justice Roberts takes into account how public opinion has shifted on the issue.

"You have 37 states and 75-percent of the population able to marry the person they love. I would think as chief justice, he will have to weigh history will judge him and the court," Bennett said.

Those against gay marriage said the questions before the Supreme Court are not so much about marriage as it is about state's rights. The Thomas Moore Society said the high court should not be deciding an issue that the conservative group views as a cultural war.

"It should be the state to determine which way we want our culture to go. There is nothing in the constitution, one vision is mandated or the other," Jocelyn Floyd, The Thomas Moore Society, said.