AD&D 2E Do you consider the Handbooks canon?

[M.L. Martin]

As for the Complete series, while 2E had a broad stance of rules being modular and up to the DM's judgement to include or exclude, generally those books (Psionics obviously excepted, as someone pointed out) were not marked Optional Rules the way so many rules in the PH and DMG (like critical hits, or XP for gold) were explicitly labeled. I just had a took through the opening pages of the Complete Fighters* and Complete Priests Handbooks to check and make sure.

They put the 'the expansion books are optional' clause in the introduction to the PHB: "Expanded character class books—The Complete Fighter’s Handbook, The Complete Thief’s Handbook, etc.—provide a lot more detail on these character classes than does the Player’s Handbook. These books are entirely optional. They are for those players who really want a world of choice for their characters." (p. 9, 1995 revision)