Final answer:
The amendment that guarantees civil rights not explicitly stated in the Constitution is the Ninth Amendment, which along with the Fourteenth Amendment, plays a crucial role in defining and protecting civil liberties and ensuring equal protection under the law.
Step-by-step explanation:
The amendment that guarantees civil rights not explicitly stated in the Constitution refers to the Ninth Amendment. Following the enumeration of specific rights in the first eight amendments, known as the Bill of Rights, the Ninth Amendment clarifies that there are additional, unenumerated rights that are retained by the people. These rights are not limited to those listed and protect freedoms such as the right to privacy, which the Supreme Court has recognized.
The Fourteenth Amendment further solidifies civil liberties by not only addressing equality in terms of the "equal protection of the laws" but also extending the protection of civil liberties to state action through its due process clause. This has been crucial in incorporating the Bill of Rights to apply to state governments and has underpinned much of the civil rights and civil liberties legislation and interpretation since its ratification.
The Fourteenth Amendment also specifically prohibits states from making or enforcing any law which shall abridge the privileges or immunities of citizens of the United States—a proclamation which bolsters citizens' civil liberties across the nation. The amendment's "equal protection clause" has been instrumental for the Supreme Court in evaluating state regulations concerning civil rights.