Not sure what you mean by "background". As I understand it, the rule of 19 (or 18, or whatever) was originally formulated as a hand evaluation guideline. It has since been adopted in regulations of some NCBOs, notably the EBU.
The regulation, for Level 2 contests in England and Wales is, from the Orange Book:
Minimum opening bids.
The minimum agreement for opening 1-of-a-suit is Rule of 19, or 11 HCP; except
You may open a natural 1-of-a-suit that may be weaker than this by agreement, but only if you do not play any conventional calls thereafter.
You may not open conventional 1-of-a-suit that may be weaker than this by agreement.
The minimum agreement for suit length for 1
is four cards; except
You may open 1
on 3 cards by agreement but only if you do not play any conventional calls thereafter.
So, while you can't (in the EBU) ignore this regulation, you aren't necessarily required to limit your 1 openings to those that satisfy the Rule of 19.
If a player habitually ignores the regulation
, let the TD know.