So when His word says "He left not Himself without a witness" and had just said that the heavens declare His Glory then He cannot lie, He has a remnant among all people and they are His witnessesFinally. Something we agree on.
God operates within the confines of His attributes. So, He does have boundaries. He can not lie, so He has no ability(power) to sin. He can not sin. Even if He tried to(though we know He will try to sin), He could not.