Constitution of the State of Ohio Art. X, § 3

The people of any county may frame and adopt or amend a charter as provided in this article but the right of the initiative and referendum is reserved to the people of each county on all matters which such county may now or hereafter be authorized to control by legislative action.  Every such charter shall provide the form of government of the county and shall determine which of its officers shall be elected and the manner of their election.  It shall provide for the exercise of all powers vested in, and the performance of all duties imposed upon counties and county officers by law.  Any such charter may provide for the concurrent or exclusive exercise by the county, in all or in part of its area, of all or of any designated powers vested by the constitution or laws of Ohio in municipalities;  it may provide for the organization of the county as a municipal corporation;  and in any such case it may provide for the succession by the county to the rights, properties, and obligations of municipalities and townships therein incident to the municipal power so vested in the county, and for the division of the county into districts for purposes of administration or of taxation or of both.  Any charter or amendment which alters the form and offices of county government or which provides for the exercise by the county of powers vested in municipalities by the constitution or laws of Ohio, or both, shall become effective if approved by a majority of the electors voting thereon.  In case of conflict between the exercise of powers granted by such charter and the exercise of powers by municipalities or townships, granted by the constitution or general law, whether or not such powers are being exercised at the time of the adoption of the charter, the exercise of power by the municipality or township shall prevail.  A charter or amendment providing for the exclusive exercise of municipal powers by the county or providing for the succession by the county to any property or obligation of any municipality or township without the consent of the legislative authority of such municipality or township shall become effective only when it shall have been approved by a majority of those voting thereon (1) in the county, (2) in the largest municipality, (3) in the county outside of such municipality, and (4) in counties having a population, based upon the latest preceding federal decennial census, of 500,000 or less, in each of a majority of the combined total of municipalities and townships in the county (not including within any township any part of its area lying within a municipality).