The freedom of communication, and mail, telegraphic, electronic, and telephonic correspondence, and other correspondence shall be guaranteed and may not be monitored, wiretapped or disclosed except for legal and security necessity and by a judicial decision.
-- From Iraqi Constitution
The conventions of a number of the States having at the time of their adopting the Constitution, expressed a desire, in order to prevent misconstruction or abuse of its powers, that further declaratory and restrictive clauses should be added, and as extending the ground of public confidence in the government will best insure the beneficent ends of its institutions, be it resolved ...
-- Preamble to Congressional Resolution Setting Forth the Bill of Rights
The preamble is remarkable because it says in a few words the basic purpose and effect of the Bill of Rights, perhaps more so than many court opinions and commentaries. The Bill of Rights (and the amendments that follow) has various functions. An important point to be remembered is that they were not supposed to imply (see the Ninth and Tenth Amendments for more discussion) that the rights were not in place already per se. Surely, many felt freedom of conscience was a natural right that no government could rightly deny, First Amendment or no First Amendment. And, “rights” is the operative word, since James Madison specifically used "shall" type language as compared to the advisory "ought" that was often used in state bill of rights.
The Bill of Rights were enacted to salve concerns of the public arising from the possibility of abuse of government power, in part because broad written phrases in the Constitution might be “misconstrued” to suggest such abuse was warranted. Also, the very declaration of the rights and principles found in the Constitution would promote and reinforce the principles found therein, serving as a guide and reminder to the people and all those who were yet to be born. And, remind us as they repeatedly are violated, since no matter how clearly they expressed, such prohibitions continue to be violated in the day to day operation of government. They were to be a sort of secular Ten Commandments, reminders of our rights and obligations, ones not always faithfully followed.
[I wrote the above elsewhere as a prologue to an expansive discussion of the Bill of Rights but darn if it bears repeating. A core value was to be declaratory, to remind the people and their government of their rights and the limits on expansive governmental powers. Said "powers" include those of the executive. This could easily be quoted -- perhaps by Sen. Byrd -- as the Alito nomination is being "debated" today.]