hi i have a web server with linux and im using my dsl connection. do you think its illegal to do that

my friend has a web server also and he is using his comcast cable high speed internet connection and he was told to remove it because they dont allow him to host a server on his house

i heard its possible to do you own domain hosting with a linux server from your home using your high speed connection like dsl but i dont know if anyone else is doing it?