16 U.S.C. § 6811 - Enforcement and protection of receipts

(a) Enforcement authority 
The Secretary concerned shall enforce payment of the recreation fees authorized by this chapter.

(b) Evidence of nonpayment 
If the display of proof of payment of a recreation fee, or the payment of a recreation fee within a certain time period is required, failure to display such proof as required or to pay the recreation fee within the time period specified shall constitute nonpayment.

(c) Joint liability 
The registered owner and any occupant of a vehicle charged with a nonpayment violation involving the vehicle shall be jointly liable for penalties imposed under this section, unless the registered owner can show that the vehicle was used without the registered owners express or implied permission.

(d) Limitation on penalties 
The failure to pay a recreation fee established under this chapter shall be punishable as a Class A or Class B misdemeanor, except that in the case of a first offense of nonpayment, the fine imposed may not exceed $100, notwithstanding section 3571 (e) of title 18.