It sounds like a paradox this phrase of Saint James, "the perfect law of liberty." Between law and liberty too often an opposition is set up by those who mistake words for ideas. In reality they are not opposed, but inter-related; they exist necessarily for each other's sake, for law implies liberty, and liberty requires law. The false idea of liberty has grown out of a false idea of law, for the connection between the two is so close and so essential that any misunderstanding of one will necessitate a misunderstanding of the other. The wise treatise of Saint Thomas Aquinas on Law, in the second part of his Summa Theologica, fixes as part of the definition of law, that it should be according to reason, ultimately according to the Divine Reason. But reason is also the very basis of liberty. I cannot freely choose, unless I can see and set in order what I have to choose and why I choose it. And liberty itself in its true meaning can also be described as signifying nothing else than an opportunity given to the will for acting according to reason. Freedom means simply that I must be able to do my duty, and freedom is always outraged whenever I am prevented from doing whatever I ought to do. The purpose then of law is to safeguard liberty, and liberty consists in fulfilling law. Liberty has nothing at all to do with privilege; privilege indeed almost always means that other people's liberty is being interfered with. An exemption from a law at least tends to become ordinarily a disregard for law.
When we approach political and social questions it is still more evident that liberty and law are inter-related. Laws are multiplied, or should be, only that liberties may be increased. Law indeed restrains, but does not thereby oppose, liberty. Law restrains others from interfering with my liberty, and me from interfering with theirs. Hence an increase in civilization must bring with it a multiplication of laws, for the need becomes more and more insistent of preventing others from hurting my freedom. Law restrains violence and creates liberty. Without it we should obviously sink back into anarchy and be at the mercy of anyone and everyone. The older philosophers, in their justification for the State, contrast with the easy and quiet life of normal times the fury of unrestrained and individual feuds, such as, they supposed, preceded the creation of tribes with codes of law. They speak of that earlier stage of the history of the race as making life "nasty, brutish, short." Whether they were historical in the surmise does not for the moment interest us. But it is clear that previously to law there could have been no liberty. Civil institutions, legislation, etc., are valuable, therefore, just in so far as they enable the will to follow reason, and are harmful in so far as they make that following impossible. That is the supreme test. Anti-religious legislation or the privilege legislation that is afforded to Catholics must be judged for their wisdom on this principle: How far do they permit a man to do his duty?
This, then, must be my ideal as a Catholic, this perception of law as safeguarding liberty, and this perception of liberty as being nothing else than the free opportunity for carrying out law. It is a state of soul, an attitude not an action, a being not a doing, for "the Kingdom of God is with you." Within the stage of my soul is acted the whole drama of life. Then only am I really free when law itself becomes the spring of action. Then only have I understood what is meant by liberty, when I have identified myself absolutely with law, when my will is absolutely absorbed in the Divine Law, which is the Divine Will and the Divine Reason. Then only have I the "glorious liberty of the sons of God," when I am so strongly impregnated with submission to the Will of God that I obey not out of fear as a servant, but out of love as a son. The spirit of Christ is just that. He was the most free of all mankind, unhampered by evil habits, denouncing without fear what called out to Him for judgement Yet with all His freedom, nay, because of it, He was absolutely obedient to the Father. "I come to do the will of Him that sent Me" comes almost motononously from His lips. He was free because law-abiding. By freedom, therefore, I must mean not indetermination or hesitancy, but a very real determination whereby all constraint to the Divine Will is removed and I become free because identified with it. Begun on earth, this freedom can only be completed in Heaven, for the Will of God can never be done on earth as it is in Heaven. But there is perfect freedom where alone our sonship is finally achieved, where we shall be truly "born of God," one with Him, where alone is finally observed "the perfect law of liberty."
- text taken from Meditations for Layfolk by Father Bede Jarrett, O.P.