You should definitely take intro classes in both. At any school, look at the requirements for a major and a minor and try to mock up a schedule, taking into account anything else you would like to include in your college experience (like study abroad).
Either major could prepare you for law school admission.
If you feel equally drawn to both as you start to study and find you have to focus on one, you might want to think about which one would be harder to do as an auto-didact. For me, that would be chemistry, so I would use college for that and fill in other gaps (in poli science and public policy) on my own.
But mostly, I would second the advice to figure out what you are really loving and why. That’ll keep you on a path that’s most likely to keep you fulfilled.