Then Samuel took the vial of oil, and poured it on his head, and kissed him, and said, Isn't it that Yahweh has anointed you to be prince over his inheritance?
"Has not the Lord anointed you?"  (1 Samuel 10:1). This was essentially an action of God, because Samuel did it in obedience to God's specific commandment.  This was an irrevocable action; and from that time forward, Saul was "the Lord's anointed," even after he had been rejected as king of Israel.