Pennsylvania constitution
Article IX: local government
Section 8

Uniform Legislation. -- The General Assembly shall, within two years following the adoption of this article, enact uniform legislation establishing the procedure for consolidation, merger or change of the boundaries of municipalities. Initiative. -- The electors of any municipality shall have the right, by initiative and referendum, to consolidate, merge and change boundaries by a majority vote of those voting thereon in each municipality, without the approval of any governing body. Study. -- The General Assembly shall designate an agency of the Commonwealth to study consolidation, merger and boundary changes, advise municipalities on all problems which might be connected therewith, and initiate local referendum. Legislative Power. -- Nothing herein shall prohibit or prevent the General Assembly from providing additional methods for consolidation, merger or change of boundaries.