There are several questions that indicate that Wizards of the Coast's organized play outlet for D&D 5e, Adventurer's League, restricts character creation to the Player's Handbook and only ONE optional rulebook (you choose which one).
E.g. you could use the PHB and Xanathar's Guide to Everything, or the PHB and Tasha's Cauldron of Everything, but not all three of them.
I think this is a wise rule, as it allows making use of all the content, and at the same time limits the nearly unavoidable emergence of broken combinations that can arise when combining ever more features and abilities in unforeseen ways.
However, looking at the Player's Guide document from the WotC AL site, I see no such limitation. Right on page 1, it says
WHAT RULEBOOKS SHOULD I USE? You can use non-optional rules found in the Player’s Handbook, the Basic Rules, and all the books listed below.
and then continues to list out pretty much everything, Volo's, Tasha's, Mordenkainen's, Fizbans, and so on.
Can someone clarify if the PHB + 1 guideline is still in effect?