WASHINGTON — Barring corporations and unions from buying political advertisements during peak election season amounts to government censorship, a Wisconsin anti-abortion group argued yesterday.

Wisconsin Right to Life is challenging a ban on corporate ads that mention candidates two months before a general election. The Wisconsin nonprofit group wants to run advertisements telling voters to contact their senators about political issues. The Federal Election Commission says the ads would influence the election.

“You’re going to outlaw everything: Rush Limbaugh, the evening news, everything because it has an electoral impact,” attorney James Bopp Jr. told a three-judge panel.

Congress passed the advertising restrictions as part of the 2002 McCain-Feingold campaign-finance law to curb the ability of advocacy groups to run attack ads that say they are about political issues. Wisconsin Right to Life says such phony ads may be banned but not at the expense of legitimate political speech.

If the group prevails, Sen. John McCain, R-Ariz., and other lawmakers fear it will open a loophole.

Wisconsin Right to Life has been fighting the law (known formally as the Bipartisan Campaign Reform Act) since 2004, when it sought to run an advertisement urging voters to contact Wisconsin Sens. Russ Feingold and Herb Kohl, both Democrats, and ask them not to hold up President Bush’s judicial nominees.

Because Feingold was running for re-election in 2004, the ad was prohibited. Wisconsin Right to Life argued that it wasn’t trying to influence an election and said the law restricted its constitutional right to petition the government.

The FEC says the government has an interest in regulating campaign speech and says the Wisconsin group isn’t harmed by the restriction because it can either not name the candidates or purchase advertisements through its political action committee, which isn’t covered by the law.

If the government prevails, the opponents said, advocacy groups will be prohibited from publicly debating legitimate political issues that arise around election time.

“It would go so far, the First Amendment would be a farce,” Bopp said.

The federal panel did not rule yesterday. It had dismissed the case, but the Supreme Court overturned the dismissal and said Wisconsin Right to Life could argue its case before the lower court.