I think the UK passed a recent law that has made circus performance animals (beyond horses) even harder to keep - least ways a friend I know who's into circus performing mentioned such a law in the last year or two).
Thing is circuses in general in the UK are almost dead; the old travelling circus is certainly not doing well; heck even over ten years ago I recall my family went to a local travelling circus and we were the only people to attend! There's a very few big ones (often in static locations) that are surviving but the circus world has changed, though its still going.
Performing animals are also very out of fashion, barring horses, and circuses also have a rather poor legacy of bad treatment which has marred their history and given a lot of fuel to the fire to stopping them having performance animals. Interestingly in the USA it seems zoos have picked up a little of that performance side with the animals; though its not as strong in the UK (health and safety + insurance + attitudes in zoos I think prevents us getting "tiger"shows and similar that the USA has in some places).
My view is half and half; I see no harm in any animal performing where such a performance is not harmful and could even be a form of general enrichment. If dogs and horses can have fun performing and doing tricks there's no reason other species cannot do likewise. However its got to be done on the animals terms and their care has to be paramount. And of course the old days of a waggon on wheels with a cage atop being the animals only home are not conductive to good treatment; though these days with the ease of long distance travel and with many circuses being more static or limited in target areas it would be more possible to have larger and more suitable enclosures.
