I still don't think the question has been answered correctly here.
Responsible pilots will have been giving briefings as long as they can remember because it is "the right thing to do".
Then someone suddenly hears that it is now a legal requirement, and asks, when did that come about?
Obviously the legal requirement was introduced because of the litigious assholes in the passenger seat and because of the increasing numbers of assholes in the left seat not bothering with any form of responsibility.
This sort of change of official policy catches responsible people by surprise, "it shouldn't be necessary, I've been doing it for years".
And the question. When was this law introduced?
It is true the world is becoming ridiculously regulated, common sense is not recognised because it can't be guaranteed to succeed. There are too many assholes out there who try to not do anything because they can't be bothered. And then demand that it must be someone else's fault when it goes wrong.
Common sense and responsibility don't matter any more.