1. No person shall enter or remain unlawfully or engage in any activity upon land which has been posted pursuant to section 11-2111 in violation of the terms of such posted signs or the terms of any written notice and warning served upon such person pursuant to subdivision four of section 11-2111.

2. No person shall post any sign prohibiting or limiting activities on land pursuant to this article, unless authorized to do so by the owner, lawful occupant or other person or organization having authority to post such lands.

3. No unauthorized person shall injure, conceal, deface or remove a sign erected and maintained as provided in section 11-2111.