The official decision a judge makes is a ruling. You can also use this word as an adjective, to describe something or someone in charge, like a ruling political party.
The group with political power in a country might be described as the ruling coalition, and the government itself could be called the ruling authority. When it's a noun, the word ruling has a legal meaning: it's the court's opinion. This definition dates from the 1550s, from the verb rule, from its Latin root regula, "straight stick or bar."