The Cammo Dudes are members of a private security firm, EG&G Technical Services, Inc., guarding the outer perimeter of Area 51. They wear camouflage outfit (hence the name), and patrol the border in white Jeep Cherokees or dark Chevy 2500 pickup trucks. They can usually be seen sitting on top of a hill near the signs at Groom Lake Road, watching traffic on the road through high-powered binoculars.
The Cammos do not have legal authority outside the restricted area, and in fact have order to avoid contact with tourists. However, if you cross the border for ANY reason, they will detain you and call the Lincoln County Sheriff to arrest you. Then the mandatory $650 fine is the least of your problems. Technically they can even shoot trespassers, although there are no known cases where this has been enforced.