Which Connecticut State organization is responsible for registering and licensing security guards?

The government entity responsible for licensing and registering of security guards, either armed or unarmed, is under the purview of the Connecticut Department of Emergency Services and Public Protection.

You can find their website at Connecticut Department of Emergency Services & Public Protection)

This government department will often be referred to by a few similar acronyms, such as CDESPP or CTDESPP or Connecticut DESPP, but all of those acronyms mean the same bureaucratic entity.