The Alien Tort Claims Act (ATCA) was originally passed as anti-piracy statute back in the 1800s. However, it came back to prominence in the 1980s. The -act states that if you are a non-US citizen your claim can be heard in a federal court, but your claim has to vis either a violation of treaty or a violation of custom.
-Filartiga: two Paraguayan citizens brought suit against Paraguayan police chief who was also living in USA. Plaintiffs alleged that the defendant had tortured and murdered a member of their family. The district court dismissed for lack of subject matter jurisdiction, holding that the law of nations does not regulate a states treatment of its own citizens. The US Court of Appeal reversed holding that the contemporary law of nations had expanded to prohibit state sanctioned torture. Court looked to universal declaration of human rights.