Both the WBF and the ACBL actively solicited opinions about possible changes to the Laws. Here are some links:
"If South held AJ76, South would always return the jack."
I think there are quite a lot of problems with that agreement. For example:
- When declarer has Q10x it saves him a guess.
- When he has K10xx and later loses the lead to his LHO, he has a second stopper ...
FWIW, the EBU's definition is
"[A] partnership understanding ... whereby the meaning of a lead, signal or discard is based in principle on information not available to declarer."
I don't find that particularly satisfactory.
Nor, I suspect do its authors, because they follow it with an exception for suit ...
This is a matter of law, not regulation.
The Laws are almost the same all over the world. There's no reference to "slip of the tongue" in either the ACBL version of the Laws or the Laws used by the rest of the world.
The relevant law refers to ...