“Self-executing” there means that the Constitutional prohibition doesn’t require Congress to pass a law on the subject.
Some Constitutional provisions do require Congressional action to take effect. For instance, the income tax is authorized by the Sixteenth Amendment, but the amendment does not itself create an income tax; it just tells Congress that it may do so.
(The original Constitution did not allow an income tax, because it expected the federal government to fund itself from tariffs and from tax assessments from the states, which were required to be proportional to population.)
“Self-executing” there means that the Constitutional prohibition doesn’t require Congress to pass a law on the subject.
Some Constitutional provisions do require Congressional action to take effect. For instance, the income tax is authorized by the Sixteenth Amendment, but the amendment does not itself create an income tax; it just tells Congress that it may do so.
(The original Constitution did not allow an income tax, because it expected the federal government to fund itself from tariffs and from tax assessments from the states, which were required to be proportional to population.)