; (2) to prevent a State from enforcing a right-to-work law that prohibits employers and labor organizations from negotiating provisions in a labor agreement that require union membership or payment of union fees as a condition of employment; (3) to preempt or limit any State law in effect on the date of enactment of this Act that provides for the rights and responsibilities described in section 4(b) solely because such State law permits an employee to appear on the employee’s own behalf with respect to the employee’s employment relations with the public safety agency involved; (4) to prohibit a State from exempting from coverage under this Act a political subdivision of the State that has a population of less than 5,000 or that employs less than 25 full-time employees