25 C.F.R. § 161.717
What happens if BIA does not collect enough money to satisfy the penalty?
BIA will send written notice to the trespasser demanding immediate settlement and advising the trespasser that unless settlement is received within 5 business days from the date of receipt, BIA will forward the case for appropriate legal action. BIA may send a copy of the notice to the Navajo Nation, permittee, and any known lien holders.