Amy Yvette Garrou, College admissions expert (US and international colleges)
To add to Michael's great advice about getting a U.S. bachelor's degree: I know that in some countries, "graduation" or "graduate" degrees are what in the U.S. we call "bachelor's" degrees. So indeed, if you wish to study law in the US (at Harvard or any other law school), you'll have to get a bachelor's degree somewhere else first. You can get a bachelor's in almost any subject, especially one in which you do a lot of reading and writing analytical papers. There are even successful law-school applicants (to U.S. law schools) who have bachelor's degrees in accounting or engineering, because these programs involve problem-solving and analysis.
In your country, it might be possible to study law directly after secondary school. If you already have a law degree and then want to apply to a U.S. law school, you'd be applying for a different degree (L.L.M.) which may not be what you need in order to practice in your country. You'll need to think about where you want to practice law later: in your country or region? or in the U.S.? If you don't have U.S.citizenship or a U.S. green card, you'd have to work for an employer in the U.S. who would sponsor you.
Here are some FAQs from Harvard Law School's website for international applicants, which explain the different types of law degrees: http://hls.harvard.edu/dept/jdadmissions/apply-to-harvard-law-school/international-applicants/frequently-asked-questions-for-international-jd-applicants/#faq-1-2
I hope this is helpful!