Because there is no federal common law, officers of the Service may lawfully make arrests for crimes not cognizable under the immigration laws only if the laws of the state or territory in which they are operating permit them as private citizens to make arrests. An officer should make an arrest as private citizen only under extraordinary circumstance for the may be used for damages if his action is unlawful under state law, regard less of his belief that it is lawful. For his own Protection he should be certain that some law, state or federal authorized him to make the arrest. (Added)