>
Then the bill of rights added a few civil liberties, i.e. rights the government specifically did not have. Theoretically this shouldn't make a difference, because anything not listed in the constitution was already unconstituional.I don't think this is true even for the strictest originalist interpretation possible. Without the Bill of Rights, Congress and the President would have much more expansive power in their creation and especially enforcement of law.
The Constitution does not establish a process for the federal government to investigate, detain, try, and punish people for violating its laws, though it is clear that it must have those powers. The major function of the Bill of Rights is to draw lines around those powers, lines that perhaps existed in the common law, but that could have been altered by Act of Congress in the absence of a constitutional provision.
There are also parts of the Bill of Rights which do constraint Congress's enumerated powers. For example, even under a strict originalist interpretation, the Commerce Clause would allow Congress to take actions that abridge the freedom of speech, religion, and assembly. It could prohibit the publishing of certain newspapers across state lines, for instance. The First Amendment prevents that kind of thing.