Let's see the toothless get ruthless 
I'm surprised. Having just read this, it turns out that the ASA has absolutely no power at all. Provided an advertisement doesn't break any laws, all they can do is ask nicely that the offending advertiser (provided it's a member of their cosy little club) please remove the advertisement if they'd be so terribly nice. If the advertiser chooses not to, then the ASA rolls out it's big guns and ..... wait for it ....... sends out a press release!!!!!
I'd expect that for a small time advertiser on the internet: maybe placing a few banner ads, created by the website owner's partner, parent(s), classmate or themselves - this doesn't sound like much of a threat. While the ASA might be able to wave the prospect of the UK print, billboard and TV media possibly withdrawing advertising space if they raise an eyebrow, I can't see the major internet advertisers caring (or even knowing) who the ASA is.
 ref. Pink Floyd: Radio KAOS