What does the 9th amendment do? Why is that important?

The Ninth Amendment protects unenumerated residual rights of the people, and, by the Tenth, powers not delegated to the United States are reserved to the states or the people. The Ninth Amendment, (1791) to the Constitution of the United States, part of the Bill of Rights, formally stating that the people retain rights absent specific enumeration. The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people. The Ninth Amendment clearly rebutted the possible presumption that enumeration of some rights precluded the recognition of others. By its terms, it provides that the enumeration of specific rights should not be “construed to deny or disparage” other rights

the qing dynasty placed strict limits on foreign merchants' ability to trade in china.