Justice is one of the four so-called cardinal virtues. She owes her place in the tarot to this. The four virtues of prudentia (prudence, wisdom), justitia (justice), fortitudo (courage, strength) and temperantia (moderation, self-control) are considered extra important in Christianity, because other virtues rely on it (cardinal means “pivotal”, based on the Latin cardo: hinge).
Noteworthy, is that the cardinal virtues, both in and outside the tarot, are almost always personified by women. The reason for this can be found in the book of Wisdom from the Old Testament. In this book these four virtues are mentioned as the result of the divine “Wisdom” (Greek: Sophia), which underlies creation:
…her [Wisdom] labours have great virtues: for she teacheth temperance, and prudence, and justice, and fortitude, which are such things as men can have nothing more profitable in life.
Sophia (Wisdom) is one of the names of God the Mother; the feminine aspect of God, which is found in the human pelvis as well as in all of creation. The yogi calls her the kundalini-shakti. This is – of course – not how the church explains Sophia, but this meaning can be inferred from the Bible texts if they are read with esoteric glasses. Another quote from the Book of Wisdom:
For wisdom [Sophia] is more mobile than any motion; because of her pureness she pervades and penetrates all things. For she is a breath of the power of God, and a pure emanation of the glory of the Almighty; therefore nothing defiled gains entrance into her. For she is a reflection of eternal light, a spotless mirror of the working of God, and an image of his goodness. Though she is but one, she can do all things, and while remaining in herself, she renews all things; in every generation she passes into holy souls and makes them friends of God, and prophets…
(Wisdom 7: 24-27)
We find Sophia – disguised – on many tarot cards. Not only as a personification of the cardinal virtues, but also as, for instance, the High Priestess.