Since the passage of the first federal estate tax laws in 1916, many difficult problems have presented themselves to the United States Supreme Court and the inferior federal courts with respect to their application. Possibly nothing in this field has caused more trouble than the decision as to whether and to what extent Congress has the power to tax retroactively gifts made in contemplation of death and transfers intended to take effect in possession or enjoyment at or after the death of the donor; and further, assuming it has such power, exactly what constitutes a gift or transfer within the meaning of the act. The decisions of both the Supreme Court and the lower federal courts leave the answer to the question in doubt.