50 Pa. Stat. § 7102
It is the policy of the Commonwealth of Pennsylvania to seek to assure the availability of adequate treatment to persons who are mentally ill, and it is the purpose of this act to establish procedures whereby this policy can be effected. The provisions of this act shall be interpreted in conformity with the principles of due process to make voluntary and involuntary treatment available where the need is great and its absence could result in serious harm to the mentally ill person or to others. Treatment on a voluntary basis shall be preferred to involuntary treatment; and in every case, the least restrictions consistent with adequate treatment shall be employed. Persons who are mentally retarded, senile, alcoholic, or drug dependent shall receive mental health treatment only if they are also diagnosed as mentally ill, but these conditions of themselves shall not be deemed to constitute mental illness: Provided, however, That nothing in this act shall prohibit underutilized State facilities for the mentally ill to be made available for the treatment of alcohol abuse or drug addiction pursuant to the act of April 14, 1972 (P.L. 221, No. 63), known as the "Pennsylvania Drug and Alcohol Abuse Control Act." Chronically disabled persons 70 years of age or older who have been continuously hospitalized in a State operated facility for at least ten years shall not be subject to the procedures of this act. Such a person's inability to give a rational, informed consent shall not prohibit the department from continuing to provide all necessary treatment to such a person. However, if such a person protests treatment or residence at a State operated facility he shall be subject to the provisions of Article III.
50 P.S. § 7102