U.S. Rep. Charlie Dent teamed with U.S. Sen. Joe Lieberman behind a proposal to revoke citizenship of Americans engaged in terrorist activities. Under the proposed bill, citizens who go abroad to work with terrorist groups could not come back into the country with a U.S. passport. But Peter Spiro, a professor at Temple's Beasley School of Law, said that argument is flawed. If federal authorities know enough about a person to revoke citizenship, then that person would also be on no-fly lists and under surveillance. ''The idea that it is going to disarm the terrorist operative is unfounded,'' Spiro said. "The bottom line here is that it's constitutional but ultimately meaningless."