I thought he was there on a work visa
Plenty of discussion on the net about this, if you look.
http://www.visaservices.duke.edu/ConstitutionalRights.html#q2
2.As an alien, not a citizen or national of the U.S., do I have Constitutional Rights?
The Constitution refers to three kinds of people to whom the Constitution applies: citizens, persons, and the people. Those distinctions mean that aliens have some rights, but not all. In looking at Constitutional Rights, note first to whom the discussion applies. But remember also that legal scholars often disagree on exactly how and to whom the Constitution applies.
3.What are some of the rights I have as an alien?
The most common ones discussed by immigration and civil rights attorneys are:
First Amendment freedom of expression
Fourth Amendment protection from unreasonable search and seizure
Fifth Amendment protection against self-incrimination
Fourteenth Amendment guarantee of "due process" or "equal protection" under the law
If you are an alien who has been admitted to the U.S., then generally you have these rights. If you entered the U.S. illegally and were, therefore, not properly "admitted," then some of the protections do not apply to you.