Supplement Four
SOC-14 5K
There are quite a few characters in 1001 characters that break it for one thing, for another it didn't exist in CT or revised CT before TTB.
A few more tidbits...
The rule is part of the Starter Traveller rule set. I did not see it listed in Book 1, though.
I checked the MT Player's Guide, since the rule is used in that edition of the rules, too, and it seems that the Player of the character is tasked with reducing his character's skills to comply with the rule before chargen is complete.
In a CT game, though, I'd still go with what I said above. If a character comes out of chargen with more total skill levels than his Experince score allows, the character's only option to improve is to increase his EDU score first, then follow the normal Experience rules.