Metal Detecting on Civil War Sites in the US

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"Scavengers have been at it again -- picking over the sacred ground of America's greatest battlefield" begins an article in a US newspaper (Torsten Ove, 'Gettysburg rangers stay vigilant for looters', Pittsburgh Post-Gazette,  July 14, 2012): 

Looters descended on Gettysburg National Military Park last weekend with metal detectors and dug 23 holes near Spangler's Spring in search of buckles, bullets, buttons and other artifacts from the three-day struggle in July 1863 that claimed 8,000 lives and changed the course of the Civil War. "We know it was a case of relic hunters," park spokeswoman Katie Lawhon said. "It's not uncommon. Two or three times a year we will find evidence that someone has done some metal detecting. Sometimes we catch the people. Sometimes they do it in broad daylight." [...] The culprits could have been professional collectors trying to sell what they found, although most artifacts aren't worth much, or they could have been casual hobbyists gathering items for themselves.

The US has laws which are supposed to prevent the removal of artefacts from a "national battlefield" and the US Park Service has control of a number of Civil War sites from Manassas, Va., to Vicksburg, Miss. The problem is that there are not enough resources to police these sites properly and it's hard to stop every collector, Gettysburg for example is a big site: "The park stretches over 6,000 acres, features 1,300 monuments and welcomes some 1.2 million visitors every year".The article then details some of those caught artefact hunting on sites like this:

In 2001, Russell Beeson was sentenced to four months in prison for stealing some 100 artifacts from Pea Ridge National Park in Arkansas, which was founded in 1956 to preserve the scene of the Battle of Pea Ridge in 1862.  Mr. Beeson used a metal detector to find and remove bullets, artillery pieces and a brass button from a Union uniform.
In 1997, Jeffery Blevins and John Walker went to prison for several months in what remains the largest Civil War-related violation of the Archaeological Resources Protection Act. Clad in camouflage, the two men stole more than 2,000 artifacts, including artillery shells and buttons, from Petersburg National Battlefield in Virginia, scene of the Siege of Petersburg that resulted in 70,000 casualties. 

And at Gettysburg itself there have been a number of incidents followed by apprehensions:

In August 2009, a maintenance man told rangers he'd seen two men with metal detectors behind the McLean House in the northwest corner of the park. Rangers responded and caught the two, identified as John Vaneman and Douglas Derrico, with metal detectors.
A search turned up 11 holes. Rangers seized the metal detectors and some relics. The case is pending.
Scavengers routinely run afoul of rangers just for having metal detectors. Federal regulations call for a $75 fine for possession of a metal detector in a national park. Rangers at Gettysburg this year have issued those fines several times. In February, two relic hunters with metal detectors were caught near Gen. George Meade's headquarters, where they had dug two holes. Last month, an Ohio man was cited for possessing a metal detector in the park. He was caught before he could start digging.

The article suggests that the hobby of artifact hunting (that's the phrase it uses) has grown in popularity with shows like "Diggers" on the National Geographic channel and Spike TV's "American Diggers".