The Constitution, specifically the Bill of Rights, contains specific provisions designed to protect individuals. The above answer notes that no bill of attainder can be passed; the same provision also prohibits ex post facto laws. However these are minuscule to the rights provided by other provisions of the Constitution:
- The First Amendment creates, in Thomas Jefferson's words, a "wall of separation between Church and State." We therefore have the liberty to worship (or not) as we please, and no religious institution is tax supported. The same amendment guarantees us freedom speech, freedom of assembly and of the press. The Supreme Court has construed this provision to also include a right of privacy.
- The Fourth Amendment protects us from unreasonable searches and seizures.
- The Fifth Amendment protects us not only from double jeopardy and being forced to testify against ourselves; but also guarantees that our property will not be taken without just compensation, nor shall we be denied life liberty or property without due process of law.
- The Sixth Amendment guarantees one a speedy public trial by a jury of ones peers; thus one need not fear secret court proceedings or lengthy incarceration without trial. One is also guaranteed the right to confront witnesses who might testify against him, including the power to compel those witnesses to testify against their will. It further guarantees one the right to an attorney.
- The seventh amendment guarantees one trial by jury in civil cases if the amount in controversy exceeds twenty dollars. Thus one might ask for a jury trial even for a traffic ticket.
- The eighth amendment protects one against excessive fines, excessive bail, and cruel and unusual punishment.
- Overarching all of these are the provisions of the Fourteenth Amendment:
No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
This Amendment has been construed to guarantee citizens of the U.S. against infringement of their rights even by the states. The Equal Protection Clause has been one of the most far reaching in U.S. Legal history. It was the basis for most Civil Rights legislation and ultimately may become the final authority in the present gay marriage debate.
Thus the founders of our Constitution went to great lengths to guarantee to every person in the U.S. the life, liberty and pursuit of happiness of which Thomas Jefferson spoke.
The Constitution does this in two main ways.
First, various parts of the Constitution and the Bill of Rights protect specific liberties. The Constitution bans bills of attainder, for example, and the 5th Amendment protects us from having our life, liberty, or property taken without the due process of law.
Second, the overall system set out by the Constitution protects us. The Constitution sets up a system of checks and balances with separation of powers. These things make it harder for the government to act. Because of this, it is harder for the government to do anything that might take away our life, liberty, or ability to pursue happiness.