Cooperative purchasing is a term used by GSA to describe the ability for state and local agencies to buy off of certain GSA Schedules.

Cooperative Purchasing allows GSA to provide states and localities access to certain items offered through the General Services Administration's:

• Federal Supply Schedule 70, Information Technology (IT), 
• Consolidated (formerly Corporate Contracts) Schedule contracts, containing IT Special Item Numbers (SINs). The information technology available to state and local governments includes automated data processing equipment (including firmware), software, supplies, support equipment, and services.
• GSA Schedule 84 (Total Solutions for Law Enforcement, Security, Facility Management Systems, Fire, Rescue, Special Purpose Clothing, Marine Craft, and Emergency/Disaster Response).

Schedule 84's products and services available to state and local governments include alarm and signal systems, facility management systems, firefighting and rescue equipment, law enforcement and security equipment, marine craft and related equipment, special purpose clothing, and related services.

For the legal minded:  

Section 211 of the E-Government Act of 2002 (the Act) amended the Federal Property and Administrative Services Act to allow for "Cooperative Purchasing." 

Public Law 110-248, the Local Preparedness Acquisition Act, amended the "Cooperative Purchasing" provisions of the Federal Property and Administrative Services Act to allow the Administrator of General Services to provide states and localities access to certain items offered through GSA's Federal Supply Schedule 84