The jurisdiction, both civil and criminal, over persons within national forests shall not be affected or changed by reason of their existence, except so far as the punishment of offenses against the United States therein is concerned; the intent and meaning of this provision being that the State wherein any such national forest is situated shall not, by reason of the establishment thereof, lose its jurisdiction, nor the inhabitants thereof their rights and privileges as citizens, or be absolved from their duties as citizens of the State.
16 U.S. Code § 480 - Civil and criminal jurisdiction
Provisions substantially in the language of this section are contained in section 12 of act Mar. 1, 1911, applicable to national forest lands acquired on the recommendation of the National Forest Reservation Commission under sections 500, 515 to 519, 521, 552 and 563 of this title.
“National forests” and “national forest” substituted in text for “forest reservations” and “reservation”, respectively, on authority of act Mar. 4, 1907, ch. 2907, 34 Stat. 1269, which provided that forest reserves shall hereafter be known as national forests.