Of Revisions And Errata

Many of my worlds (and FuzzyGeff) are what we called "nexus" worlds.  These worlds allowed the players to use their imaginations and make a character from any background they pleased.

As always there were limitations put on what Tech Levels were available, how common magic was and if there was any psionics at all.

In my more permissive moments I'd allow anything, but GURPS 3e(R) has about 80 books, I wasn't going to carry all of them every time just to support a single player's desire to do something different.

One time in particular a player wanted to play a psi.  No problem, this is allowed.

When characters were finished, I would always check the math to make sure my campaign assumptions were being followed.  This character was made with the Psionic book instead of the Basic Set psi rules so I asked him for the book.  He handed it over and the point totals were wrong.  "Fix it," says I.

He looks over his character sheet with a confused expression and asks, "fix what?"
"Those levels are five points each, not three."
"Oh!  That was changed in the second release of the book."  FuzzyGeff even stepped up to confirm that the rules were, indeed changed in a newer printing of the book.
"Then put a copy of that book in front of me.  You know my rules, if it's a book I don't bring or own, you have to prove it by showing me the text.  The text you handed me disagrees with what you're saying; and I don't doubt you, but proof is required or you know that somebody will cheat."
"But it's not my book that's here..."
"If you run home and bring it to me before we start, you can use it."

He refused to make the trip and was resentful about being forced to adhere to the rules he'd handed me.

Need I mention that this was one of the players who'd been caught cheating before?