SAN JUAN, Puerto Rico (AP) -- Jennifer Efron is a U.S. citizen because
                  she was born in Puerto Rico. But her parents say Puerto Ricans' U.S.
                  citizenship is not guaranteed, so they're asking the U.S. Supreme Court to
                  allow the teen-ager to naturalize.

                  If the Supreme Court agrees to hear Efron's petition, the case could affect
                  millions of Puerto Rico-born citizens both in this Caribbean territory and on
                  the U.S. mainland.

                  Efron's attorneys argue that since Congress granted residents of Puerto Rico
                  a statutory U.S. citizenship in 1917, it technically could revoke it --
                  especially if the island eventually should become independent.

                  That prospect is remote -- less than 5 percent of island voters have
                  supported independence in recent plebiscites. Still, the possibility that Puerto
                  Rico's status as a U.S. territory could change "makes the concern (over
                  citizenship) even greater," attorney Nathan Dershowitz said Thursday.

                  "There's millions of people in the United States who don't know what their
                  status is," said the New York-based Dershowitz, whose brother, celebrity
                  lawyer Alan Dershowitz, also is on Efron's legal team.

                  Puerto Rico has a population of nearly 4 million. At least 2 million others
                  who were born in Puerto Rico live on the U.S. mainland.

                  Officials at the U.S. Immigration and Naturalization Service insisted
                  Thursday that Puerto Ricans' citizenship rights are not at risk.

                  "The bottom line is that a person born in Puerto Rico is a U.S. citizen and
                  does not need to be naturalized," INS spokesman Bill Strassberger said.

                  The U.S. District Court for the Southern District of Florida and the U.S.
                  Eleventh Circuit Court of Appeals ruled the same way in dismissing lawsuits
                  filed by Efron's father, David Efron.

                  But in an article last year, former U.S. Attorney General Dick Thornburgh
                  said that Puerto Ricans' citizenship is "granted by statute and not fully
                  protected by the U.S. Constitution."

                  To date, the Supreme Court has not considered any case that would clarify
                  the issue. Efron said Thursday the Supreme Court has several months to
                  decide whether to hear his appeal.

                  As a U.S. commonwealth, Puerto Rico enjoys limited autonomy. The
                  island's U.S. citizens are eligible for military service and receive billions of
                  dollars in U.S. federal aid each year, but they cannot vote for president and
                  have only a non-voting congressional representative.

                  Supporters of U.S. statehood for Puerto Rico have tried to sell statehood as
                  the only guarantor of U.S. citizenship.

                  David Efron, father of 15-year-old Jennifer, is a statehood advocate, and he
                  acknowledged his petition could have wide-reaching political implications.

                  "This is more than a case. It's a cause," said Efron, a native of Cuba and San
                  Juan attorney and real estate developer who became a U.S. naturalized
                  citizen as a child.

                  Efron said he fears recent frictions in Puerto Rico's relationship with the
                  United States are signs of a changing political climate that puts Puerto
                  Ricans' U.S. citizenship more at risk.

                  The Puerto Rican government has demanded that the U.S. Navy leave its
                  training ground on the island of Vieques after a fatal accident in April. And
                  many in the United States were angry that President Clinton offered
                  clemency in August to 16 pro-independence Puerto Rican activists affiliated
                  with a militant group blamed for deadly bombings in New York and Chicago
                  in the 1970s and 1980s.

                  "With everything that's been going on with the Puerto Rican prisoners and
                  Vieques, there's a lot of nationalistic sentiment (among Puerto Ricans),"
                  Efron said. "I don't know what the U.S.' take is on this."