It is not legal, the gardai cars there are trying to stop the race. The gardai are, for lack of a better description, afraid to do anything to the travelling community. Unfortunately the travelling community have a really bad name, and are not readily accepted by most of the country. The majority of people are more or less afraid of them.
Julie - they don't race on tracks because there are (often) dodgy dealings going on behind these races. Unregistered gambling, using pain masking drugs, ect. A lot of these races are for bragging rights more so than anything else.
The ISPCA and the IHWT do their best to try and cull these events, but for the most part it is "advertised" through word of mouth among the community. We have a halting site in a town close to us, and there are horses who are not in the best of condition in the field beside it. Is anybody willing to go in to check them out? Not a hope. They are far too concerned about their own safety.