Don - no one ever tells anyone what they can and cannot sing. It's a complete red herring. I was at a folk club the other night whose MC told me in fairly stern terms, at the start of the night, that they were very much on the traditional side of things. Two hours later I'd heard Rose of Allendale, Farewell to the Gold, a couple of Kiplings and several original songs.

I started a thread a few years back asking for first-hand experiences of the "Folk Police" - i.e. organisers telling a performer that they shouldn't sing song X, because it wasn't Genuine Folk. I think one person came up with a story that fitted; mostly the only prohibition anyone could remember was of incompetence - and that was pretty rare.