Yes, ruling is a Scrabble word!

Verb

1. Exercise authority over; as of nations

2. Decide with authority

3. Be larger in number, quantity, power, status or importance

4. Decide on and make a declaration about

5. Have an affinity with; of signs of the zodiac

6. Mark or draw with a ruler

7. Keep in check

Adjective

1. Exercising power or authority

Noun

1. The reason for a court's judgment (as opposed to the decision itself)