Final answer:
The constitutional right that neither the federal government nor the states can restrict, except the right to marry, since it's not explicitly protected by a specific amendment as the right to vote is under the Fifteenth, Nineteenth, and Twenty-Sixth Amendments.
Step-by-step explanation:
The question seeks to identify which of the listed items is not a constitutional right that is protected from restriction by both the federal government and the states. Looking at the options provided, the right to marry, the right to privacy, and the right to free exercise of religion are all rights that have been recognized by the Supreme Court as being protected by the Constitution. However, these rights are not explicitly enumerated in the original text of the Constitution but are found within its interpretation, particularly through the Due Process clause of the Fourteenth Amendment and other judicial precedents. On the other hand, the right to vote is expressly protected by several amendments (the Fifteenth, Nineteenth, and Twenty-Sixth Amendments), which explicitly restrict both federal and state governments from denying the right to vote on the basis of race, sex, and age, respectively.
The correct answer is, therefore, Option (a) The right to marry, because unlike the right to vote, it is not specifically safeguarded against abridgment by any particular constitutional amendment that applies to both state and federal governments. It's important to note, however, that through cases like Loving v. Virginia and Obergefell v. Hodges, the Supreme Court has recognized the right to marry as a fundamental right protected by the Due Process and Equal Protection Clauses of the Fourteenth Amendment, but it is not a specifically enumerated right protected against the actions of both the federal government and the states.