I don think there is specific legislation to curb web scraping, however the general laws like copyright act and the contract act would give the person aggrieved by web scrapping to move the court for injunction and also for the damages caused.
secondly the terms and conditions of the web site would be applicable reserving the right to the owner of the site to sue for web scrapping, how ever the owner has to show that data has been scrapped from his website causing damages.