In early 2016, the active duty map pool included classic versions of Dust II, Mirage, Inferno, Cache, Train, Overpass, and Cobblestone.
A legal gray area exists for users who owned CS:GO on Steam before it was deleted. In theory, you can download depots via Steam's console commands (if you have the manifest IDs) and then apply a NoSteam emulator to run them. This is technically more legal than downloading a pre-cracked repack from a torrent site. Counter Strike Global Offensive v.1.35.2.2-NoSteam