B. an important victory for the abolition movement
The Amistad was a Spanish ship on 1839 that kidnapped people from Africa to be sold into slavery in Cuba. While en route, some slaves escaped, and killed most of the crew. The ship ended up in America in New York.
Spain and Cuba wanted the people returned to Cuba to be enslaved. The US Supreme Court found that since they were illegally enslaved, they were free, and should be returned to Africa.
