Vegetarians pushed for stricter welfare requirements, but then did not buy the product. English people for a long time were buying Danish bacon, thinking it was higher quality. (Luckily, Danish farmers voluntarily moved to higher welfare standards, and now English bacon has got a better reputation.)
> So it's actually more effective to have low welfare requirements that are only slightly better than those abroad in order to keep prices competitive so that people buy from the farms with marginally better conditions.
I think it's better to have decent welfare standards, and then to educate consumers about the differences between local farms and distant farms. Scandals like the "horse meat in ready meals" help to educate consumers about the importance of knowing where meat is produced.
Import duties are also helpful, but there are problems with world trade organisations.