But if his general concept is to work in a policy shop related to government it will be important to have education related to the area of policy. If it is in economic policy, then a background in economics is important. If it would be foreign relations, in the State Department for instance, then a background in history or economics would likely be helpful. Graduate work in a major publid policy school is a huge plus, such as the Kennedy School at Harvard or the Sanford Institute at Duke.
One thing you could do is some web browsing. Go to the Dept of Defense and State. Each have a section under "About Us" with "Biographies" of the senior leadership. Read those of people that seem to have positions he might find interesting. I think their backgrounds will be enlightening. They are quite varied, and usually quite impressive.
Do the same at think tanks like Rand, Hoover, CSIS, CNAS. They , too, will have similar backgrounds, and in many cases are the people that have populated or will populate the jobs you look at under the DoD or State.
One thing you will notice when you go through those is the conspicuous lack of lawyers. At least at the higher levels, a law degree wouldn't be of much use.
That isn't to say that a lot of people working in state and local governments, or in legislative positions aren't lawyers. But if high end public policy is the goal, law school isn't the route.