March 8 (Reuters) - The Republican National Committee on Thursday lost a bid to dissolve a decades-old legal agreement with the Democratic National Committee over the GOP's use of improper election tactics.

The agreement dates to 1982, when the Republican National Committee settled a lawsuit brought by the Democratic National Committee accusing the GOP of trying to intimidate minority voters. Under the agreement, the Republican National Committee must obtain court approval before implementing certain poll-monitoring activities in minority precincts.

The Republican Party filed suit in November 2008 to void the agreement. But the Philadelphia-based U.S. Court of Appeals for the 3rd Circuit rejected the GOP's request on Thursday, affirming a New Jersey district court's ruling.

"If the RNC does not hope to engage in conduct that would violate the Decree, it is puzzling that the RNC is pursuing vacatur so vigorously," Judge Joseph Greenaway wrote on behalf of the three-judge panel. He noted that the party sought to escape the decree at a critical moment, in time for the upcoming election cycle.

The original lawsuit, filed in 1981, accused the RNC of mailing sample ballots to registered voters in minority districts, and then using any postcards returned undeliverable for voter challenges. The suit also accused the Republican Party of posting off-duty police officers at polls in minority precincts, some with visible firearms. Under the settlement agreement, the GOP had to obtain court approval before using any ballot security measures in minority districts.

In 2008, the RNC went back to court to lift the agreement. The party argued that the risk of voter fraud had increased, justifying stronger prevention measures. They argued that the political landscape had shifted, with more minority-voter turnout and African Americans serving as president, attorney general and chair of the Republican National Committee. Moreover, the suit claimed the decree violated the Republican Party's free speech rights.

But the New Jersey district court and the 3rd Circuit refused to cancel or weaken the decree.

Parties can waive their First Amendment rights in private agreements, the appeals court held. And the argument pointing to African Americans in office "hardly requires a serious response," Greenaway wrote.

The 3rd Circuit affirmed the lower court's modifications to the decree, including an added expiration date of Dec. 1, 2017.

Bobby Burchfield, a lawyer for the Republican National Committee, said in an email that the ruling underestimates the public's interest in preventing voter fraud. It also allows Democrats to allege decree violations on the eve of an election to disrupt Republican operations, he said.

Angelo Genova, a lawyer for the Democratic National Committee, praised the ruling. "The Third Circuit reinforced the efficacy of the Consent Decree, which has for three decades provided protections against minority voter suppression throughout the nation," he said in an emailed statement.

Election law professor Richard Hasen at University of California, Irvine described the ruling as a "huge win" for the Democratic Party. He said the Republican National Committee could file an emergency appeal to Supreme Court Justice Samuel Alito, who oversees the 3rd Circuit. Alternately, the committee could seek review by the full 3rd Circuit.

Impersonation fraud, which the ballot security measures target, is only a small fraction of voter fraud, the court noted in its opinion. More common types of fraud include corruption among election officials or attempts to manipulate absentee ballots, said Hasen, who has written a forthcoming book on the subject.

The case is Democratic National Committee et al v. Republican National Committee et al, U.S. Court of Appeals for the 3rd Circuit, No. 09-4615.

For the Democratic National Committee: Angelo Genova of Genova, Burns & Giantomasi.

For the Republican National Committee: Bobby Burchfield of McDermott Will & Emery.

(Reporting By Terry Baynes)

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