There is only one known reference to the Law of Ascension 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.
Although the law is mentioned specifically only once, there are many references to “Ascension,” for example:
A Master learns the meaning of each confining form; then He assumes control and wields the law upon the plane consistent with the form. He has then outgrown the form and discards it for other and higher forms. Thus, He has progressed always by means of the sacrifice and death of the form. Always, it is recognised as imprisoning, always it must be sacrificed and die so that the life within may speed ever on and up. The path of resurrection presupposes  crucifixion and death, and then leads to the mount whence Ascensionmay be made.
The Resurrection and Ascension, the final triumph which enables the initiate to sing and to know the meaning of the words: “Oh death, where is thy sting? Oh grave, where is thy victory?” [xxiii] 21