4 Pa. Code § 249.55
The pension benefits available to State employees under the code may only be changed, modified or altered by legislation. No collective bargaining agreement, or binding arbitration award, or any determination resulting from the collective bargaining process between the Commonwealth and its employees, or between other employers whose employees are subject to these provisions, shall have the effect of modifying, altering or changing any benefit specifically provided under the code, unless there is statutory authority authorizing such change, alteration or modification. The repealer provisions of the code specifically exclude, as a bargainable matter under the act of June 24, 1968 ( P. L. 237, No. 111) (43 P. S. § § 217.1-217.10), with respect to collective bargaining between policemen and firemen, and the Public Employee Relations Act (43 P. S. § § 1101.101-1101.2301), with respect to collective bargaining between public employers and their employees, those items relating to the pension benefits provided by the code.
4 Pa. Code § 249.55