MIAMI — A judge in the Florida Keys overturned the state's constitutional ban on same-sex marriage on Thursday after a legal challenge by gay couples said it effectively made them second-class citizens.The ruling by Circuit Judge Luis M. Garcia applies only to Monroe County, which primarily consists of the Keys, and will certainly be appealed. The lawsuit contended that the same-sex marriage ban approved overwhelmingly by voters in 2008 violated the federal 14th Amendment's guarantee of equal protection under the law. The judge said licenses could not be issued until Tuesday at the earliest.Attorney General Pam Bondi and ban supporters argued that the referendum vote should be respected and that Florida has sole authority to define marriage in the state. The Florida amendment defined marriage solely as a union between one man and one woman."The court is aware that the majority of voters oppose same-sex marriage, but it is our country's proud history to protect the rights of the individual, the rights of the unpopular and the rights of the powerless, even at the cost of offending the majority," Garcia wrote in his decision. "Whether it is ... when Nazi supremacists won the right to march in Skokie, Illinois, a predominantly Jewish neighborhood; or when a black woman wanted to marry a white man in Virginia; or when black children wanted to go to an all-white school, the Constitution guarantees and protects ALL of its citizens from government interference with those rights."Gay marriage proponents have won more than 20 legal decisions around the country since the U.S. Supreme Court struck down the federal Defense of Marriage Act last year, although most of those rulings remain in various stages of appeal. Many legal experts say the U.S. Supreme Court may ultimately have to decide the question for all states.Currently, 19 states and the District of Columbia have legalized same-sex marriage.During a recent hearing on a related Florida case in Miami-Dade County, attorneys for gay couples noted that, after a long legal fight, the state finally allowed them to adopt children but refused to recognize them as married."That inequality stigmatizes the couples and their children as second-class citizens," attorney Sylvia Walbolt said. "Same-sex marriages are completely beneficial. They are entitled to the full protection of the Constitution."Supporters of the gay marriage ban focused mainly on the 2008 referendum vote rather than whether same-sex marriages were harmful or beneficial. Anthony Verdugo, executive director of the Christian Family Coalition, said it was wrong for a single judge to overrule the will of a majority vote."The people of the state have the right to decide," Verdugo said.Along with the similar lawsuit pending in Miami-Dade, a separate lawsuit is pending in a federal court in Tallahassee seeking to force Florida to allow gay marriage and recognize same-sex marriages performed in other states.Florida has long been a battleground over gay rights. In the 1970s, singer and orange juice spokeswoman Anita Bryant led a successful campaign to overturn a Dade County ordinance that banned discrimination against gays. The county commission reinstated the ban two decades later.Florida in 1977 became the only state that prohibited all gay people from adopting children. A state court judge threw out the law in 2008 when she found "no rational basis" for the ban when she approved the adoption of two young brothers by Martin Gill and his male partner. The state decided two years later not to appeal that ruling, making gay adoption legal.The amendment Garcia overturned Thursday was passed by a 62-38 margin in 2008 and banned both same-sex marriage and domestic partnerships.