The Federalist Interpretation of the Ninth Amendment has some merit, but the Amendment still protects natural rights.
One of the criticisms made against originalism by historians is that originalism fails to take into account that word meanings change over time. In particular, historians argue that during important periods, such as the time leading up to the Constitution, word meanings changed. Therefore, originalism is problematic because it assumes that traditional word meanings are stable.
Unfortunately, this charge by historians turns out to be largely mistaken. If some originalists assume that word meanings were stable, then that would be an argument against those originalists. But it would not condemn originalism generally, since nothing in originalism requires that word meanings be stable. And in fact, I believe very few, if any, originalists assume that words meanings are unchanging.
How does originalism properly address the issue of changing meanings? If an originalist were seeking to interpret a constitutional term, then the originalist would look to the meanings that existed at the time of the Constitution. If the traditional meaning continued to exist at that time, then that would certainly be one possible meaning. But a good originalist would also look and see if a new meaning had developed. If a different meaning had developed, then of course the originalist would consider that as another possible meaning.
If there were two possible meanings, that would mean the term was ambiguous. The originalist should them employ the interpretive rules at the time to resolve the ambiguity. One consideration in choosing between the two meaning is which one was more common. Another would involve the evident purpose of the provision. A third would be the structure of the document. There are, of course, others.
The criticism of originalists for assuming stable meanings are often wide of the mark. It is sometimes claimed that the originalist argument, which maintains that the Executive Power Vesting Clause provides the President with a limited foreign affairs powers, assumes stable meanings. But this is not true.
This originalist interpretation argues that the language vesting the executive power in the President provides him with the powers that executives, such as the King of England, typically enjoyed in the 18th Century, minus the executive powers that were given to the Congress (such as the power to declare war) and minus the executive powers that were limited in other ways (such as the power to appoint executive officers, which was to be exercised only with the advice and consent of the Senate).
While this interpretation relies on the traditional meaning of executive power, it does not simply assume that meaning continued. It shows that this meaning fits the structure of the Constitution, providing for an interpretation that fully accounts for the foreign affairs powers of the federal government. And it also shows that the traditional understanding of executive power continued to be used in the Philadelphia Convention itself as well as after the Constitution was adopted by officials as different as Thomas Jefferson and Alexander Hamilton.
Stable meanings certainly make the job of originalist interpretation easier. But good originalism does not assume that they exist and originalist interpretation can be done without them.