Anyboday know if B1 Visa could travel in US without problem?

A friend with B1 Visa want to visit me, I want to know if he can travel around in US?

It was said there is law prohibit B1 from travel in US?
Can the guy with B1 visa travel by plane inside US?

BOW!

I did not think there is any problem. Travel within US, he will not be checked by anyone from INS.