It is an affirmative defense to prosecution under this division that:
(1) A building or occupied structure involved in an offense under section 14-71 was abandoned; or
(2) The premises were at the time open to members of the public and the actor complied with all lawful conditions imposed on access to or remaining in the premises; or
(3) The actor reasonably believed that the owner of the premises or other person empowered to license access thereto would have licensed him to enter or remain; or
(4) The actor was in the process of navigating or attempting to navigate with a nonpowered vessel any stream or river in this state and found it necessary to portage or otherwise transport the vessel around any fence or obstructions in such stream or river.
State law reference--Similar provisions, R.R.S. 1943, 28-522.