If you say that you are not ruling in a particular course of action, you mean that you have not definitely decided to take that action.
We have made no decisions on restructuring yet. We are ruling nothing out and we are ruling nothing in...
We must, as I said, take care not to rule in or rule out any one solution.
PHRASAL VERB : usu with brd-neg , V n P , V P n (not pron)