Before I was saved I denied the right of Jesus to reign in my life. When I was saved I recognized it and yielded my heart to it. Since then I have broken plenty of his laws, but that he is Lord and ruler of me, there is no doubt.
That is the situation with most of us. But that is not what advocates of Lordship salvation teach. They take scripture like Luke 14:33 quite literally,
So likewise, whosoever he be of you that forsaketh not all that he hath, he cannot be my disciple. (Luke 14:33)
If you do not forsake all that you have,
If you do not sell all that you have,
If you do not give all to the poor,
If you do not take up your cross,
If you do not deny yourself of all,
If you do not all of the above, and more, then you cannot be saved.
That is a works based salvation. It is also legalism. Legalism is adding to the grace of God that brings salvation. It was dealt with in Acts 15 when the Judaizers (legalists) wanted to add the keeping of the law and circumcision to the simple gospel message of grace by faith. McArthur and others are adding the above stated works to that same simple message, so that it is no more by grace but of works.
Receive not the grace of God in vain.