If I were to analyze an electronic device and reproduce the circuit schematics, would it be legal to publish the schematic?
I know that there might be issues with selling a clone but I am not so sure of the schematics themselves.
Yes, unless your acquisition of the device was under a license containing restrictions on your use, such as non-disclosure, or reverse engineering, your publication of schematics would not necessarily violate that license, let alone patent laws or copyright laws applicable to the general public.
Patent laws mainly permit the owners to prevent you from making, using, selling or importing an infringement (or inducing infringement) and copyright laws do not cover any "idea, procedure, process, system, method of operation, concept, principle, or discovery". 17 USC § 102(b).