It would be better to see the full context, but I strongly suspect that what you are referring to is a provision or opinion to the effect that state law controls the question cited and that no city, town or county may regulate concerning them.
The general question of "preemption" arises in a hierarchical governmental system, and involves the issue of whether a lesser level of government may enact a statute (or equivalent) with respect to the same subject as an enactment of a superior level of government.
Preemption has two prongs.
Prong 1 (the easy one): no lesser government may enact a provision that conflicts with or would hinder the enforcement of a provision enacted by a higher level of government.
Prong 2 (the not so easy one): no lesser government may enact any provision with respect to a subject of regulation as to which it is determined (by a court or by express provision of the superior enactment) that the superior level of government has "occupied the field."
Preemption is usually studied in the context of the federal vs. state relationship, but it applies equally to the state vs. locality relationship.
Disclaimer: the foregoing summarizes in a couple of short paragraphs a subject on which entire legal textbooks have been written. It is necessarily very general.