The President of the United States may from year to year in his discretion under such regulations as he may prescribe authorize the Indians residing on reservations or allotments, the fee to which remains in the United States, to fell, cut, remove, sell or otherwise dispose of the dead timber standing, or fallen, on such reservation or allotment for the sole benefit of such Indian or Indians. But whenever there is reasonable cause to believe that such timber has been killed, burned, girdled, or otherwise injured for the purpose of securing its sale under this section then in that case such authority shall not be granted.