There is no law regarding audience recording. The live renditions of the songs themselves are property of players and authors, which are in this case both Iron Maiden. EMI, Sanctuary, or whatever company publishes their official works has nothing to do with it. So if the band says go ahead, it's good. However, the band can change that decision anytime, and stop all bootlegs from being legally shared.
Tapping into soundboards and video feeds is another issue, more from a property usage standpoint. TV, webcast and radio based bootlegs are based on a public broadcast anyway. Even video bootleg compilations, where you have recordings of various TV programs and shows, are based on public broadcast. But here lies a potential issue, because you have additional entities claiming rights for bootlegged material, from media houses themselves, that particular show owners, etc.
Third category would be foreign market bootlegs, for instance there's a Maiden England Japanese laser-disc rip, that's being shared inside bootleg community, despite of source being official recording. This made sense back when bands didn't have world-wide publishing or digital distribution, example would be no Accident Of Birth release in Brazil. That doesn't make it a less of a rip-off, since some 3rd company is making money from band's official material, but without it people would have little means to hear songs.
So, audience recordings are fine as long as the band agrees. Pro-shot stuff could be challenged on court, but there's really no point, and I don't think it ever happened. Foreign market bootlegs could be taken off-line by cease and desist order immediately.