The U.S. Supreme Court 's . arguments on Tuesday over same-sex marriage will cap more than . two decades of litigation and a transformation in public . attitudes . Based on the court 's actions during the past two years , a. sense of inevitability is in the air : That a majority is on the . verge of declaring gay marriage legal nationwide . Justice Anthony Kennedy , the court 's pivotal member on gay . rights , has been marching in this direction with opinions dating . to 1996 . In his most recent gay rights decision for the court in . 2013 , rejecting a legal definition of marriage limited to a man . and woman for purposes of federal benefits , Kennedy deplored . that U.S. law for making gay marriages 'unequal . ' Scroll down for video . A moment in history : People line up outside the Supreme Court in Washington April 26 ahead of Tuesday 's arguments focusing on gay marriage . That 5-4 decision did not address a constitutional right to . same-sex marriage , but lower court judges interpreted the ruling . as an endorsement of it and began invalidating state bans . When states appealed rulings striking down their same-sex . marriage prohibitions , the Supreme Court declined to intervene , . most notably in October 2014 when it denied appeals in seven . cases on a single day . Instead , the nine justices are hearing in Tuesday 's oral . arguments an appeal of the sole decision from a regional U.S. appeals court that went the opposite way . Last November , the . Cincinnati-based U.S. Court of Appeals for the 6th Circuit . upheld gay marriage bans in Ohio , Michigan , Kentucky and . Tennessee . With 37 of the 50 states now permitting gay marriage , many . because of judicial orders , it seems unlikely the country 's . highest court would reverse course . Public opinion polls over . the last decade have shown large increases in support for gay . marriage . A ruling is due by the end of June . Yet some questions remain . How much will Kennedy , a member of the court 's five-man . conservative bloc who often casts decisive votes in close cases , . show his hand in the 2-1/2 hours of oral arguments ? Will he . reveal a clear view that the Constitution gives gay people a. right to marry or will he voice concerns for state interests in . controlling marriage laws ? An element of uncertainty hovers over Chief Justice John . Roberts , who broke with the other court conservatives and cast . the deciding vote upholding President Barack Obama 's healthcare . law in 2012 . Roberts voted against gay rights in the 2013. ruling . But he separated himself from the most conservative . dissenters and declined to declare outright that states may ban . gay marriage . He has demonstrated apprehension about the reputation of the . court that , by virtue of his service as chief justice , . informally bears his name . In his opinions , he has sometimes . tried to lower tensions in controversial cases and reassure . people that the court is aligning with precedent and public . expectations . The question is not only how Roberts might vote but what he . might write . In the 2013 ruling , he denounced the court majority 's . sentiment that federal lawmakers were deliberately harming gay . people with the limited definition of marriage . ' I would not tar . the political branches with the brush of bigotry , ' he wrote . For the other seven justices , expectations are clearer . The four liberals , Ruth Bader Ginsburg , Stephen Breyer , . Sonia Sotomayor and Elena Kagan , have signaled their opposition . to state same-sex marriage bans . On the other side have been the . three most conservative justices , Antonin Scalia , Clarence . Thomas and Samuel Alito , asserting that nothing in the . Constitution guarantees same-sex marriage . Two legal questions are before the justices : whether the . Constitution 's guarantees of due process and equal protection . cover a right to same-sex marriage ; and , if they do not , whether . states that ban same-sex marriages must recognize such unions . performed in other states . Gay couples and their families , about 30 adults and 20. children , have appealed the 6th Circuit 's decision . The name . petitioner is James Obergefell , who wanted his home state of . Ohio , which prohibits gay marriage , to recognize his Maryland . marriage to John Arthur as Arthur was dying from amyotrophic . lateral sclerosis , also known as Lou Gehrig 's disease . Officials expect the courtroom to be packed to its 400-seat . capacity . Lines for general spectator seats began forming around . 6am on Friday , more than four days ahead of the scheduled . oral arguments at 10am on Tuesday .
Top US court is expected to hear arguments in a gay marriage case Tuesday . A majority vote could make gay marriage legal viable . The court will hear a ruling by June .