Section 31.21 - Transfer of permit(1) No transfer or assignment of any permit granted under s. 31.06 or 31.08 shall be of any effect whatsoever unless it is in writing and a certified copy thereof within 10 days after the execution thereof, is filed with the department and unless such transfer or assignment is approved in writing by the department; and no such transfer or assignment shall be approved by the department except after an investigation and a finding that the transfer or assignment is not made or intended to be made for a purpose or to create a condition prohibited by s. 196.665 and that the transferee or assignee has complied with s. 31.14(2) or (3). No permit shall be transferred or assigned to a foreign corporation, nor shall any permit granted to a municipality be assigned or transferred to any person, otherwise than as security for a loan made in good faith and concurrently with and as consideration for such transfer or assignment, and no foreign corporation shall have power to acquire title to any such permit, nor shall any person have power to acquire title to a permit granted to or acquired by a municipality, otherwise than in the enforcement of such security, and in no case shall any such foreign corporation hold title to or operate under any such permit for a period longer than 3 years.(2) No municipality shall make or execute any lease or other contract with any person, firm, or corporation for the sale or use of hydraulic or hydroelectric power developed or generated by such municipality under a permit granted under s. 31.06 or 31.08 for a period longer than 10 years, unless the same shall be first approved by the department, after investigation and upon a finding that such lease or contract will not impair or interfere with the purpose or uses for which such dam was acquired or constructed by the municipality.