Just compensation shall be paid by the removing authority upon the removal of any of the following signs which are not then in conformity with this division whether or not removed pursuant to or because of this division:
(1) Signs lawfully in existence on February 10, 1972.
(2) Signs lawfully in existence on land adjoining any highway made an interstate or primary highway after February 10, 1972.
(3) Outdoor advertising signs, displays, or devices erected with the purpose of their message being read from the main-traveled way of any interstate highway or primary highway erected outside of an urban area and beyond 660 feet of the edge of the right-of-way of an interstate or primary highway erected prior to April 11, 1978, and not otherwise lawful under Section 23-1-273.
(4) Signs lawfully erected on or after February 10, 1972.
Notwithstanding any provision of law to the contrary, no removing authority shall remove or cause to be removed, or cause the alteration in any manner of, any lawfully erected sign along any public street or highway within the state without paying just compensation. Amortization for whatever period shall not constitute just compensation.