I started using prong collars on both my dogs a couple of months ago, and it has made all the difference in the world. Though they are well-trained and heel quite nicely, when they saw cat or squirrel or any prey, with belt collars I was either dragged down the street on my face or was forced to drop their leads.
With the prong, when they feel any pressure they drop back to give me a loose lead. They now beome excited when I bring out the prongs because they know we're going somewhere fun.
As far as legalities in your country, no clue. If they are illegal, it's truely a shame as they are a very good training tool.