The Supreme Court is wading into the fight over same-sex marriage at a time when public opinion is shifting rapidly in favor of permitting gay and lesbian couples to wed, but 40 states don't allow it.

The court's first major examination of gay rights in 10 years begins Tuesday with a hearing on California's ban on same-sex marriage. On Wednesday, the justices will consider the federal law that prevents legally married gay couples from receiving a range of benefits afforded straight married Americans.

Actor-director Rob Reiner, who helped lead the fight against California's Proposition 8, was at the head of line Tuesday morning. Some people waited since Thursday - even through light snow - for coveted seats for the argument.

The two California couples challenging the voter-approved ban on same-sex marriage in the nation's largest state also are at the court for the argument and are urging the justices to strike down not just the California provision, but constitutional amendments and statutes in every state that define marriage as the union of a man and a woman.