It's Legal!
This is a direct copy/paste from the SCCA Solo Rules:
AIR CONDITIONING
Stock class cars with optional air conditioning are allowed to
compete without the belt in place. Additionally, the entire air
conditioning system may be removed, but any related components
(springs, radiator, etc.) that are part of an air conditioning package
must be returned to standard parts for the standard model (non-air
conditioned). Removal of part of the air conditioning system is
allowed only if no other components for the car differ between
model’s equipped with and without air conditioning, i.e., springs,
radiator, etc.
Air conditioning may be added to any car as a “comfort and
convenience” item, provided it serves no other purpose and other
components are not added or deleted unless otherwise authorized
by the current Solo Rules.
If a factory option, may be removed and backdated as an assembly
or separate components of the system may be removed (i.e.,
individual under-hood components only).