And it is also immaterial that the intrusion was in aid of law enforcement. Experience should teach us to be most on our guard to protect liberty when the Government’s purposes are beneficent. Men born to freedom are naturally alert to repel invasion of their liberty by evil-minded rulers. The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well meaning but without understanding. Olmstead v. United States, 277 U.S. 438 (1928) (Brandeis, J., dissenting), overruled by Katz v. United States, 389 U.S. 347 (1967).

The protection guaranteed by the Amendments is much broader in scope. The makers of our Constitution undertook to secure conditions favorable to the pursuit of happiness. They recognized the significance of man’s spiritual nature, of his feelings, and of his intellect. They knew that only a part of the pain, pleasure and satisfactions of life are to be found in material things. They sought to protect Americans in their beliefs, their thoughts, their emotions and their sensations. They conferred, as against the Government, the right to be let alone — the most comprehensive of rights and the right most valued by civilized men. To protect that right, every unjustifiable intrusion by the Government upon the privacy of the individual, whatever the means employed, must be deemed a violation of the Fourth Amendment. And the use, as evidence in a criminal proceeding, of facts ascertained by such intrusion must be deemed a violation of the Fifth.

[Olmstead v. United States, 277 U.S. 438 (1928) (dissenting)]

An avidity to punish is always dangerous to liberty. It leads men to stretch, to misinterpret, and to misapply even the best of laws. He that would make his own liberty secure, must guard even his enemy from oppression; for if he violates this duty, he establishes a precedent that will reach to himself. Thomas Paine. Paris, July, 1795.

Supreme Court Justice Thurgood Marshall argued in another context many years later, the “grave threats to liberty often come in times of urgency, when constitutional rights seem too extravagant to endure.

Whereas it appeareth that however certain forms of government are better calculated than others to protect individuals in the free exercise of their natural rights, and are at the same time themselves better guarded against degeneracy, yet experience hath shewn, that even under the best forms, those entrusted with power have, in time, and by slow operations, perverted it into tyranny; and it is believed that the most effectual means of preventing this would be, to illuminate, as far as practicable, the minds of the people at large, ....whence it becomes expedient for promoting the publick happiness that those persons, whom nature hath endowed with genius and virtue, should be rendered by liberal education worthy to receive, and able to guard the sacred deposit of the rights and liberties of their fellow citizens, and that they should be called to that charge without regard to wealth, birth or accidental condition of circumstance.

Though eternal vigilance is sage advice, surely “wartime” (or when politicians would try to convince us that it is such a time) is when those who value the preservation of individual liberty must be most on guard.

He that would make his own liberty secure must guard even his enemy from oppression; for if he violates this duty he establishes a precedent that will reach to himself.

The Constitution was made to guard the people against the dangers of good intentions

History teaches that grave threats to liberty often come in times of urgency, when constitutional rights seem too extravagant to endure.

I was, indeed, aware that a jealous, ever-waking vigilance, to guard the treasure of our liberty, not only from invasion, but from decay and corruption, was our best wisdom and our first duty.

I fear you do not fully comprehend the danger of abridging the liberties of the people. Nothing but the very sternest necessity can ever justify it. A government had better go to the very extreme of toleration, than to do aught that could be construed into an interference with, or to jeopardize in any degree, the common rights of its citizens.

Let us be clear at the outset that the liberty of individuals to carry on their business should not be abrogated unless the larger interests of the many are concerned. It is the purpose of government to see that not only the legitimate interests of the few are protected but that the welfare and rights of the many are conserved. These are the principals which must be remembered in any consideration of this question. This, I take it, is sound government-not politics.

It is proper to take alarm at the first experiment on our liberties. . . . The freemen of America did not wait till usurped power had strengthened itself by exercise, and entangled the question in precedents. They saw all the consequences in the principle, and they avoided the consequences by denying the principle. We revere this lesson too much, soon to forget it. . . .

Liberty may be endangered by the abuses of liberty as well as by the abuses of power.