Under the Ohio Constitution a city must obey all state laws unless it has a charter. This is also known as Home Rule. A charter is essentially the Constitution of the city. A city charter is, of course, subservient to the Ohio and United States Constitutions. The purpose of a charter is to allow the citizens of a city the opportunity to customize some laws as needed by their community. If a charter specifically authorizes "something" that is normally against state law and that "something" affects only the community with the charter, then the charter makes that procedure it legal for that city.

An example of a lawful change would be the how extra credit points are calculated for Civil Service Examinations. An example of an unlawful change would be the raising of the blood alcohol limit used to determine whether a driver is drunk to a number greater than permitted by Ohio law.

Important: If a state law is to be overridden in a community, it must specifically be included in the charter. A City Council in a chartered city cannot override a state law simply by passing a new, conflicting ordinance. Unfortunately some try anyway. 

Always keep this truism in mind: A government can do anything it wants until a court of law says it must stop.