It's not the first time that this has happened, even before all the tightening of regulations, and artists who haven't got the requisite work permits have had real problems on arrival at this country. My other half has just come back from a month in California, and had to get all the paperwork spot on before she could go.

It's not really a question of whether the rules are excessive, stupid, bureaucratic, etc. (and I also happen to think they are). The onus is always on the artist(e) or their agency or manager - whoever - to work out the requirements before the journey is made, and make sure they're complied with. It's a huge shame that Allison Crowe was refused entry, but you can't buck the system just because you're a performer, and ignorance of the system is no excuse.