A conservative gadfly lawyer who has made a career of skewering Democratic administrations is taking his battle against the National Security Agency's telephone surveillance program to a federal appeals court.

Activist attorney Larry Klayman won the first round in December, when U.S. District Judge Richard Leon, a Republican appointee, ruled that the NSA's surveillance program likely runs afoul of the Constitution's ban on unreasonable searches. The government appealed.

In court filings in preparation for Tuesday's argument, the Justice Department told three Republican-nominated appeals judges that collecting the phone data is of overriding and compelling importance to the nation's security.

Former NSA systems analyst Edward Snowden revealed the phone data collection effort a year and a half ago, triggering a debate over privacy rights and surveillance.

In New York, the U.S. Court of Appeals for the 2nd Circuit recently heard arguments in an appeal of a judge's opinion that found the surveillance program legal.

The three appeals judges in the Washington case have generally come down on the government's side on national security issues.