US Civil War battlefield looted,

Metal detectorists "researching the site" (ie identifying potential "productive areas") is producing the loot for them to pocket, but is eroding the historical record (Andreas Preuss, 'Civil War battlefield looted, described as 'crime scene' CNN May 28, 2016):

The National Park Service is calling part of a Civil War battlefield "an active crime scene" following a series of excavations. Authorities are investigating looting at the Petersburg National Battlefield, just south of Richmond, Virginia. The battlefield describes itself as the site of the war's longest siege, lasting nine months between 1864-1865, and claiming 70,000 casualties. "Earlier this week, one of the park employees was out doing landscape work and noticed some things were out of place," NPS spokesman Chris Bryce said. The looting happened in the eastern part of the park, the National Park Service said, citing a large number of excavated pits. Marked graves were not disturbed. Park officials have not described what type of items or relics were stolen in the theft. "They are probably doing their homework of the area, probably did research on Civil War ...They were in the ground, they likely would have used a metal detector and a digging tool," Bryce said. Civil War relics, like uniform buttons, rifle parts and other metallic battlefield items regularly show up on internet auction sites. The Park Service says looting a National Battlefield is a federal crime, carrying up to a $20,000 fine and two years in prison for a conviction. 

Setting up a Portable Antiquities Scheme here would solve nothing. Destruction is destruction.