What is the legality of attempting to call someone with an unlisted number?

I want to talk to someone with an unlisted number. He has not directly told me not to contact him, but mentioned his wife would if she ever found unknown numbers on his bill. No he has not contacted me with the numbers where I can contact me, he is pretty non-conional. He says he hopes we never have to end our friendship (non-ual), but will not go against his wife. He is a pretty timid person due to his culture. I want to maintain our friendship, as a man he understands the tightrope I am going through trying to live an arranged marriage in a society where women can pick and choose. Still, I don't want him to have problems.