Two self-anointed "grammar vigilantes" who toured the nation removing typos from public signs have been banned from national parks after vandalizing a historic marker at the Grand Canyon.

Jeff Michael Deck, 28, of Somerville, Mass., and Benjamin Douglas Herson, 28, of Virginia Beach, Va., pleaded guilty in U.S. District Court in Flagstaff after damaging a rare, hand-painted sign in Grand Canyon National Park. They were sentenced to a year's probation, during which they cannot enter any national park, and were ordered to pay restitution.

According to court records, Deck and Herson toured the United States from March to May, wiping out errors on government and private signs. On March 28, while at Desert View Watchtower on the South Rim, they used a white-out product and a permanent marker to deface a sign painted more than 60 years ago by artist Mary Colter. The sign, a National Historic Landmark, was considered unique and irreplaceable, according to Sandy Raynor, a spokeswoman for the U.S. Attorney's Office in Phoenix.

Deck declined comment, and Herson could not be reached.

An affidavit by National Park Service agent Christopher A. Smith says investigators learned of the vandalism from an Internet site operated by Deck on behalf of the Typo Eradication Advancement League, or TEAL. Smith identified four members, but only Deck and Herson faced charges.

According to the Internet posting, TEAL members agreed to "stamp out as many typos as we can find, in public signage and other venues where innocent eyes may be befouled by vile stains on the delicate fabric of our language."

Deck's diary account of the Grand Canyon incident was submitted as evidence in court. It says the two men climbed Desert View Watchtower while on holiday from their typo-enforcement duties "and discovered a hand-rendered sign inside that, I regret to report, had a few errors. I know today was supposed to be my day off from typo-hunting, but if I may be permitted to quote that most revered of android law enforcers, Inspector Gadget, 'Always on duty!' I can't shut it off. . . . Will we never be free from the shackles of apostrophic misunderstanding, even in a place surrounded by natural beauty?"

After correcting a misplaced apostrophe and comma, Deck reported, he was aghast to discover what he described as a made-up word: "emense."

"I was reluctant to disfigure the sign any further, so we had to let the other typo stand. Still, I think I shall be haunted by that perversity."

Deck's quest to clean up punctuation, language and spelling mistakes was featured in various media before the Grand Canyon episode.

The Dartmouth graduate told reporters he became passionate about grammar after winning junior-high spelling bees.

His Web site now contains only a cryptic message: "I write. I also edit. Perhaps I could be of some service to you."

There is a link to TEAL's home page, which says only that a public statement is forthcoming.

A separate link to Deck's resume has been blocked. Photos from the episode, extracted from another Internet site, also were submitted as evidence.

In addition to being banned from national parks for a year, the defendants, who pleaded guilty to conspiracy to vandalize government property, are banned from modifying any public signs. They also must pay $3,035 to repair the Grand Canyon sign.