It may as well be the 11th Commandment: Leave nature as you found it, the National Park Service says.
So imagine the horror of a little girl named Eve -- no, Evie, to be exact -- when she violated the Eden that is Yosemite National Park.
Her sin: She took home two sticks.
Park Ranger Matt Holly learned of this transgression during a routine day opening hundreds of letters from visitors awed by Yosemite.
The handwritten note from Evie read:
"Dear Park Rangers,
"I am a Yosemite Junior Ranger. I went to Yosemite recently and accidentally brought home two sticks. I know I'm not supposed to take things from the park, so I am sending them back. Please put them in nature.
Touched by her innocence, Holly taped the two sticks to her letter and temporarily hung it over his desk.
It's been hanging there for almost a year, he said.
"We all loved it," the public information officer told CNN this week. "It was so moving to see how small the sticks were."
He contacted the family, who are park regulars, and told them of how Evie's note moved all the park rangers.
They are now preparing to reunite the sticks with their home.
"I think we are about ready to return them to where they belong, back in nature," Holly said. "The family comes here often, they know a lot about the park and she kind of knows where she wants them."
Evie's letter is now being considered for display in Yosemite's visitor center or elsewhere, Holly said.
The U.S. Department of Interior may already have its caption. On its Twitter account this week, the agency commented about the letter of apology from the junior park ranger, a title given to youths between ages 7 and 13 who complete a program while visiting a national park. It said:
"Cutest. Story. Ever."