Despite the popular support, Judge Walker found that the measure was rooted in "unfounded stereotypes and prejudices" and that the plaintiffs in the case -- one lesbian and one gay couple -- demonstrated by "overwhelming evidence" that it violates rights to due process and equal protection under the Constitution.
The case, which will likely reach the U.S. Supreme Court, is one that experts say has the potential to transform social and legal precedent.
They compare the potential impact to the famous 1954 Brown v. Board of Education decision, which desegregated schools, and the 1967 Loving v. Virginia decision, which ended laws banning interracial marriage.
"This case reflects a classic tension between democratic values," said Ben Bishin, a political science professor at University of California-Riverside. "People often think that democracy means the will of a majority should be law, but its also about equality and liberty. Questions of minority rights speak to values of equality and liberty, and courts are reluctant to tread on those rights when there's no harm done to society."
A recent California Field poll found that 51 percent support legalizing gay marriage with 42 percent opposed.
Nationwide, public views are more narrowly divided, according to the most recent ABC News/Washington Post poll. Forty-seven percent of Americans polled favor gay marriage while 50 percent are opposed.
Five states -- Massachusetts, Iowa, Connecticut, Vermont and New Hampshire -- and the District of Columbia perform same-sex marriages. Four states recognize marriages performed elsewhere and nine states grant civil unions or partnerships.