PA. CONS. STAT. ANN. tit. 62, §1901. Definitions
The following words and phrases when used in this chapter shall have the meanings given to them in this section unless the context clearly indicates otherwise:
“Cooperative purchasing.” Procurement conducted by or on behalf of more than one public procurement unit or by a public procurement unit with an external procurement activity.
“External procurement activity.” A buying organization not located in this Commonwealth which if located in this Commonwealth would qualify as a public procurement unit. An agency of the United States is an external procurement activity.
“Local public procurement unit.” A political subdivision, public authority, tax-exempt, nonprofit educational or public health institution or organization, nonprofit fire company, nonprofit rescue company, nonprofit ambulance company and, to the extent provided by law, any other entity, including a council of governments or an area government, which expends public funds for the procurement of supplies, services and construction.
“Public procurement unit.” A local public procurement unit or a purchasing agency.
PA. CONS. STAT. ANN. tit. 62, § 1902. Cooperative purchasing authorized
A public procurement unit may either participate in, sponsor, conduct or administer a cooperative purchasing agreement for the procurement of any supplies, services or construction with one or more public procurement units or external procurement activities in accordance with an agreement entered into between the participants. The Department of General Services is authorized to enter into cooperative purchasing contracts solely for the use of local public procurement units or state affiliated entities. The department shall enter into cooperative purchasing contracts for the use of local public procurement units or state-affiliated entities if the number of contractors under a previously existing contract for the same supply or service is reduced to a single contractor or reduced by more than 50% of the number existing on September 30, 2003, and shall award such contracts pursuant to section 517 (relating to multiple awards) using an invitation for bids. Nothing in this section shall prohibit a local public procurement unit or state — affiliated entity from participating in or procuring from other cooperative purchasing agreements awarded by the department. Cooperative purchasing may include, but is not limited to, joint or multiparty contracts between public procurement units and open-ended purchasing agency contracts which are made available to local public procurement units.
Link to the full statute can be found here: www.legis.state.pa.us/WU01/LI/LI/CT/PDF/62/62.PDF