A reader writes:

Perhaps you help clarify something for me. We know that some "private revelations" are indeed false and we are to test the spirits to see if they are in line with the Gospel. Sometimes, we have for example, apparitions like Our Lady of Roses which the Church flat out rejects (and with good reason). However, lets's assume this was a demonic trick and not just a woman seeking attention. This false apparition, in the context of its message did admit the Lordship of Jesus, something it shouldn't be able to do. "No one can say Jesus is Lord except by the Holy Spirit.". Instead it encouraged disobedience to the Church of Our Lord. Obviously, it seems demons can use truth to aid a larger lie when it suits them. The question is then: how can they admit, even though their goal is to distort the truth, that Jesus ultimately has Lordship over them?

I think it's a serious misreading of Paul to think he means that evil spirits (or evil humans) are somehow magically unable to mouth the words "Jesus is Lord". The gospel itself records encounters with demons who profess the deity of Jesus and even speak of his saving mission:

And immediately there was in their synagogue a man with an unclean spirit; and he cried out, “What have you to do with us, Jesus of Nazareth? Have you come to destroy us? I know who you are, the Holy One of God.” (Mk 1:23–25)
And demons also came out of many, crying, “You are the Son of God!” But he rebuked them, and would not allow them to speak, because they knew that he was the Christ. (Luke 4:41).
As we were going to the place of prayer, we were met by a slave girl who had a spirit of divination and brought her owners much gain by soothsaying. She followed Paul and us, crying, “These men are servants of the Most High God, who proclaim to you the way of salvation.” And this she did for many days. But Paul was annoyed, and turned and said to the spirit, “I charge you in the name of Jesus Christ to come out of her.” And it came out that very hour. (Acts 16:16-17)

And more than this, Jesus specifically says that people can call him "Lord, Lord" but still not be his disciples:

“Not every one who says to me, ‘Lord, Lord,’ shall enter the kingdom of heaven, but he who does the will of my Father who is in heaven. On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ And then will I declare to them, ‘I never knew you; depart from me, you evildoers.’ (Mt 7:21–23).

So I think there is nothing magical about the phrase "Jesus is Lord" that prevents either humans or devils from tossing it about to lie through their teeth when they seek to deceive. Indeed, the normal pattern through history has been for liars and deceivers to say "Lord, Lord" about Jesus while ignoring the teaching of Holy Church. Precisely the measure of whether someone is saying "Jesus is Lord" by the Holy Spirit is his or her willingness to surrender their judgment to the teaching of the Church. As Jesus says to his apostles (and the popes and bishops who succeed them), "He who hears you hears me, and he who rejects you rejects me, and he who rejects me rejects him who sent me.” (Luke 10:16). If a claimant to private revelation says "Lord, Lord" but does not do what Jesus commands through his bishop, stay far away. The measure of really saying "Jesus is Lord" lies not in our empty chatter, but as Jesus says, in doing the will of his Father in heaven. If a seer will not obey his or her bishop, they are disobeying God. That is why the false claims of Maria Divine Mercy and the frauds of Medjugorje should be ignored, despite the "Lord, Lord" veneer of God talk they use as a smokescreen.  They have been disobedient to Holy Church and have taught others to do likewise.