The only known reference to the Law of Adjustment or of Balance by Alice A. Bailey (AAB) in her voluminous writings and those given to her by Djwhal Khul (DK). Links on these pages of The Laws of Alice A. Bailey are to the online books at the Lucis Trust website.
What is a law?
… a law is but the spiritual impulse, incentive and life manifestation of that Being in which he lives and moves. A Treatise on White Magic , INTRODUCTORY REMARKS
A law is an expression or manifestation of force applied, under the power of thought, by a thinker or group of thinkers. Discipleship in the New Age, Vol. I , SECTION ONE – DISCIPLESHIP IN THE NEW AGE – Part 2
… a law is in reality the effect of the life of a greater entity as it encloses a lesser within its living processes. Esoteric Healing , Part Three – The Fundamental Laws of Healing
… a law is but the effect of the continued intelligent activity of the Life aspect as it works in conjunction with matter. Esoteric Psychology – Volume I , 5. The Rays in Cyclic Manifestation
A law is only an expression or manifestation of force, applied under the power of thought by a thinker or group of thinkers. Esoteric Psychology – Volume II , II. The Seven Laws of Soul or Group Life – Part 5
A law presupposes a superior being who, gifted with purpose, and aided by intelligence, is so coordinating his forces that a plan is being sequentially and steadily matured. A Treatise on White Magic
Quotes I found below:
This law is, as we know, the basic law of all manifestation, and the paramount law for this solar system. It might strictly be called the Law of Adjustment or of Balance, for it conditions that aspect of electrical phenomena which we call neutral. The Law of Economy is the basic law of one pole, that of the negative aspect; the Law of Synthesis is the basic law of the positive pole, but the Law of Attraction is the law for the fire which is produced  by the merging during evolution of the two poles. From the standpoint of the human being, it is that which brings about the realisation of self-consciousness; from the point of view of the subhuman beings it is that which draws all forms of life on to self-realisation; whilst in connection with the superhuman aspect it may be stated that this law of life expands into the processes conditioned by the higher law of Synthesis, of which the Law of Attraction is but a subsidiary branch.
You are welcome to post your comments and understanding of this law.