IANAL, but I doubt that that is an issue in most jurisdiction. A website does not get to make their own law by simply putting up a note. Neither are the terms of use a binding contract between two parties because the scrapers are not the websites customers, and thus did not sign or agree to anything.
Wikipedia has some insight into the legal issues with web scraping: https://en.wikipedia.org/wiki/Web_scraping#Legal_issues
At least for me it looks like one are better of adding technical counter measures against scrapers then to try a legal route.