whether the bans are or are not constitutional. bob redell is live with a preview. this ruling could reopen the door for prop 8. >> reporter: the u.s. supreme court work were to rule against gay marriage, then yes, those against same-sex marriage could try to bring back prop 8, which if you recall is a california ban on same-sex marriage that vot voters approved back in '08 before it was knocked down in 2013. what the supreme court is considering now is the legality of marriage bans in four states. kentucky, michigan, ohio and tennessee. it's possible that the justices could rule those bans unconstitutional effectively forbidding any state from banning same-sex marriage and making gay marriage legal throughout the land. or the supreme court could lead this issue up to the individual states to decide. and as i mentioned, possibly reopen the fight for prop 8 here in california. as it stands, 36 states