In the UK it's not illegal per se, but if you go by the letter of the law you could be convicted under the Computer Misuse Act for it. But at the same time you

In the UK it's not illegal per se, but if you go by the letter of the law you could be convicted under the Computer Misuse Act for it. But at the same time you could be convicted for sending a HTTP GET request to a server you don't have permission to access - this law is rather broad. I'm not sure if there's even been a case to test it though, and as the general population becomes more tech savvy it seems unlikely such a conviction would be made for port scanning on it's own.