This article from the BBC says the ASA “banned” showing a pregnant nun eating ice cream with the tag line “immaculately conceived”. Wikipedia says the ASA is a non-governmental self-regulating body of the advertising industry, with no government funding or authority.
How, then, does what is essentially a non-profit organization ban ads? Is it just journalistic shorthand for: “banned member companies from running the ads,” or similar? If the ice cream company went ahead and printed these ads up and distributed them itself, would the ASA have any authority to do anything about it?
When it comes to broadcast advertising and things, one of the conditions the government puts on broadcast licenses is that they obey ASA decisions. In a case like this, it’s enforced by the CAP member organizations, and if the ice cream company printed and distributed the ads themselves, the ASA couldn’t do much, I don’t think. Here’s their sanctions page explaining it all:
If the advertisers choose to ignore the ASA, they can be referred to Ofcom or Trading Standards (depending on which applies) which are regulatory bodies.
The ASA is pretty much an intermediate step of self regulation of the industry, as you say.
Just like in the USA, where the MPAA is a private group that gives out ratings to movies. No legal or governmental authority at all. But since nearly all the theatres showing movies in the country have agreed to abide by their rules regarding ratings and what ages are admitted to see them, it works. It’s just a voluntary agreement of theatre owners to abide by the ratings given by MPAA.