

Taro Yamamoto, left, campaigns in Tokyo before a lower-house election. Nippon News/Corbis

Now, with the election just days away, he is busy excising it. Mr. Aoto is making sure stump-speech schedules and other materials on the party website are scrubbed of candidates' names and photos. On Dec. 4, he even asked party leader Mizuho Fukushima to delete a tweet in which she mentioned a candidate by name.

The self-censorship stems from a 1950 law that lays out—in great detail—what candidates for public office can and can't do in the official campaign period before election day. Feeding supporters lunch is a no-no, but tea and light snacks are permitted. Leafleting is OK, but no more than two kinds of fliers and only up to 70,000 pieces per candidate.

The law, which was aimed at ensuring no candidate or party got an advantage because they were better funded or staffed, predates—and never directly addresses—things like email, social networking and SMS text messaging.

But it has been interpreted to forbid nearly all digital electioneering, making it a huge obstacle in the Internet era, when politicians like Shinzo Abe, Japan's front-runner for prime minister, routinely post comments on Twitter, and voters look to websites for everything from policy statements to the address of party headquarters.

"It's been said that the established parties spent ¥35 billion ($420.3 million) on advertising during the last election, yet my petty election campaign tweets are banned?" said Japan Restoration Party chief and Osaka mayor Toru Hashimoto, in a Dec. 5 tweet. "What's wrong with Japan?"

Attempts to revise the law have stalled in Parliament. That has left Japanese electoral politics in a digital backwater in contrast to countries like the U.S., where the Internet has become so important to campaigning that companies like Twitter Inc. and Facebook Inc. offer politicians tutoring on social-media strategy.

Parties and candidates have tried various ways to push the envelope. On the final day of the 2009 campaign period, the Social Democrat's Mr. Aoto streamed video online of a speech by one of the party's candidates—without actually showing the candidate.

Instead, he aimed the camera at the listening crowd, so visitors to the site could hear—but not see—the speaker: technically in compliance with the "no images'' rule. Mr. Aoto thought about doing it this year, too, but decided it didn't get enough viewers to be worthwhile.

Actor Taro Yamamoto, who is running for a lower-house seat against the son of former Tokyo governor Shintaro Ishihara, stopped tweeting on Dec. 3, the day before the campaign period started.

But first he urged people to follow another Twitter account called the "Yamamoto Taro bot," which continued to churn out an automated rotation of Mr. Yamamoto's old tweets.

"Let's get the Ishihara family out of politics. Let them travel around at leisure, on a yacht," read one post.

Your Party rolled out on Facebook a widget that let visitors "vote'' on various questions and see the responses totaled up on a graph. They had to shut it down on Dec. 3, after the Internal Affairs Ministry warned them it was in the gray area.

Many of Japan's biggest parties have warned candidates to stop blogging, tweeting and friending for the duration of the campaign.

A few have halted all digital communication with the public and are taking queries only by telephone and fax. Politicians have been spending the 12-day campaign period before the Dec. 16 election parsing rules written nearly a decade before the invention of the silicon chip.

"It's really confusing," said Mr. Aoto in his cramped basement office one day recently, leafing through a book titled "Internet Election Guidelines.''

One interpretation of the law holds that streaming audio of a candidate's speech over the Internet is OK, even though uploading the text of that same speech is illegal.

But letting visitors to the website click a "play'' button to start the audio could be illegal, too, the book warned. That was news to Mr. Aoto, who said he had stuck such a "play" button on the Social Democrats' site during the 2009 election.

"In the end, it's OK as long as you don't get busted," he says.

Breaking the law is punishable—in theory—by as much as two years in jail and a maximum fine of ¥500,000. But enforcement is spotty.

The National Police Agency says it has issued 164 warnings and made five arrests for Internet-related election violations.

Japan's Internal Affairs Ministry, the chief interpreter of the law, says online text and images depicting candidates and campaigns are out, as is updating candidate Web or Facebook pages.

Text and photos of politicians who aren't running in the election are permissible, so long as they don't refer to those who are. Audio is legal, since it isn't "literature or images.''

The rules get more Byzantine deeper down in the weeds. Sending out a blank email with an audio-file attachment of a candidate speech should be OK—unless the sender's address contains the candidate's name.

Tagging a candidate in a photo uploaded to Facebook shouldn't be a problem—as long as the tagger isn't a party operative, explains Democratic Party of Japan official Haruo Semba.

Takaharu Motoyama, who ran for a seat last year in the Fukuoka city assembly in southwestern Japan, says he couldn't get arrested even though he tried. Mr. Motoyama says he had hoped to get charged with violating the Internet ban so he could take the case to court and force a ruling that would clarify the issue.

The 30-year-old elderly care worker posted speeches on YouTube and asked for support on his blog and on Twitter.

He made daily campaign pitches on a popular online video-streaming site, and put a bar code on his campaign posters that would take people who scanned it with their cellphones to his website—another violation.

But after months of quizzing by police and prosecutors, authorities dropped the case, telling him they weren't confident they could get a guilty verdict, Mr. Motoyama says.

The Fukuoka prosecutor's office says it left off only after "taking things into consideration."

As for Mr. Yamamoto, he says he doesn't know who created the bot that tweeted on his behalf. He says he is sticking by the Internet ban himself, so there won't be a blot on his record should he actually get elected.

Write to Alexander Martin at and Yoree Koh at