P.S. Pictograph Vandalism ‘Irritating’

In this Feb. 22 photo, graffiti is seen over ancient Indian pictographs at the Red Elk Rock Shelter south of Hells Gate State Park, in Lewiston. Federal officials say they are sending a team of investigators to look into vandalism of some ancient tribal pictographs near Lewiston’s Hells Gate State Park. (AP Photo/Lewiston Tribune, Eric Barker)

• Update: 3 men suspected in pictograph vandalism /Lewiston Tribune
  

In her Moscow-Pullman Daily News editorial today, Tara Roberts writes: “The red-pigmented paintings of animals and shapes at the Red Elk Rock Shelter pictograph site near Lewiston are between 200 and 2,500 years old. They tell the stories of the Nez Perce Tribe and possibly other tribes who passed through the area - people whose art and stories are integral to local history and the identities of the people who live here now. But someone recently covered those paintings in crude, pointless graffiti featuring names, initials and marijuana references. This vandalism is more than irritating. It’s an assault on a priceless piece of culture and history.” More here .

Question: What would be the proper punishment for the vandal(s) who did this?