101 Pa. Code § 21.36
Where a statutory provision is performing an active function there is an increased likelihood that it will be either cited in a judicial decision or amended by the General Assembly. Thus the failure of a statute to be either cited or amended during the 30-40 year period prior to the drafting of the revision should alert the drafting attorney to the possibility that the provision may be omitted. Under 1 Pa.C.S. § 1973 (relating to no implied repeal by nonuser) the mere failure to use a statutory provision does not affect its validity. The question is whether the failure to cite the statutory provision results from the fact that the provision has been supplied, and thus repealed, by another later statute on the same subject; or that the provision is obsolete.
101 Pa. Code § 21.36