A large group of same-sex marriage supporters was expected to gather at 6th and University avenues at about 6 p.m., then begin marching.
In his 136-page ruling, Federal District Court Judge Vaugh Walker decided that Proposition 8, the voter-approved ban on same sex marriage passed in 2008, is unconstitutional. There were about 18,000 same-sex couples married before Prop 8 passed in November of 2008.
A representative from the San Diego Lesbian, Gay, Bisexual and Transgender Community Center said he was pleased by Walker's ruling.
"We're really thrilled and believe it's a tremendous day for any and all Americans who believe that the U.S. Constitution guarantees equal protection and due process under the law," Carlos Marquez said.
But Walker ruled that the law violates the Constitutions's equal protection clause. He also said the side against gay marriage seemed motivated by little more than ill will or a sense of superiority of traditional couples over same sex couples.
To some supporters of Proposition 8, that reasoning by the judge is extremely offensive.
"When a judge tells his fellow citizens in the state of California that their vote doesn't count -- and essentially they don't count -- that their view is nothing but bigotry, that's a very serious thing for a judge to say, and he has no cause to say that," said Jennifer Roback Morse of the Ruth Institute National Organization for Marriage.
NBCSandiego asked for people to weigh in with their opinions on the judge's reasoning, and, for a while, the responses were in agreement with Walker's decision.
"Oh, heck ya," posted Cathie Gee on Facebook. "My 30-year marriage is only less valid when all can't marry."
Eventually, though, opponents of the judge's decision, including Virginia Gina Chandler, had their say.
"No, the people of CA voted twice on this, and the judge decides on his own to overturn what the voters want," Chandler posted. "Don't our votes count anymore? What happened to democracy?"
San Diego Mayor Jerry Sanders, who opposed Prop. 8, is expected to be a part of the rally at the LGBT Center.