That's how it's worked so far, and that's my prediction of how it's likely to keep working. I could be wrong, and I hope I am.
It happened to a bluegrass session in Stansted Mountfitchet up the road from us only this year, which had been going for years.
Then the authorities started leaning on the landlord, because there were more than two people playing. When he tried to get a PEL to cover it, the council insisted on all kinds of modifications of the premises, so that it just wasn't on. Reluctantly he had to tell them to stop coming to play, so he didn't have to make the modifications.
The point I was making about Kim Howells' statement was that, even if the new law is exactly in line with it - and there's no reason to trust that it will be, they've wriggled out of even more explicit promises than that - it could still leave all the room in the world for this kind of nonsense.
The Musicians Union proposal makes far more sense - that would mean that a licence to run a pub would automatically include the right to allow people to make music, subject only to the requirement that there is no risk to public safety, which could include, for example, laying down a maximum number of people in the place, and that there is no public nuisance.
This would place music-making in the same situation as any other activity in a pub, such as talking to friends, or watching the TV.