What is the difference between law (Recht) and justice (Gerechtigkeit)?

Law is objective: the laws and rules in force, man-made and valid whether or not those affected find them just. Justice is subjective: the moral standard by which situations, actions or laws are judged, tied to fairness, equality, human dignity and morality.

Everyday language uses the two in the same breath, but legal philosophy separates them sharply.

• Law (objective). The tax law is law even if many people consider it unjust. Its validity does not depend on anyone's sense of fairness.
• Justice (subjective). A philosophical and ethical goal. A ruling is felt to be just when it takes into account how the parties involved are affected.

So a law can be unjust, and a just outcome may not be required by any law. That gap is exactly where ethical debate about laws, such as surveillance laws, takes place.

Go deeper:

• Wikipedia: Justice — the main theories of justice.