They do not do it under the Ninth. They never have.
Having the power to define rights, and what is and isn't a right, under the Ninth is their Holy Grail.
That is really a stretch. Even the most fervant supporters of judicial activism do not even mention the Ninth Amendment because, as the Constitution is interpreted today, the courts can claim have all the power they wish under the 5th and 14th. If the Ninth Amendment is their "Holy Grail", than the Due Process and Equal Protection clauses are like having Jesus in their living room.