“Liberty is absence of restraint. Freedom is participation in government.”

Mont Saint Michel and Chartres (1904)
Context: No one ever seriously affirmed the literal freedom of will. Absolute liberty is absence of restraint; responsibility is restraint; therefore the ideally free individual is responsible only to himself. This principle is the philosophical foundation of anarchism, and, for anything that science has yet proved, may be the philosophical foundation of the Universe; but it is fatal to all society and is especially hostile to the State. Perhaps the Church of the thirteenth century might have found a way to use even this principle for a good purpose; certainly the influence of Saint Bernard was sufficiently unsocial and that of Saint Francis was sufficiently unselfish to conciliate even anarchists of the militant class.

p, 125
Other writings, The Paradoxes of Legal Science (1928)

Source: Libertarianism: A Political Philosophy for Tomorrow, (1971), p. 10

Political Disquisitions (1774)
Context: That government only can be pronounced consistent with the design of all government, which allows to the governed the liberty of doing what, consistently with the general good, they may desire to do, and which only forbids their doing the contrary. Liberty does not exclude restraint; it only excludes unreasonable restraint. To determine precisely how far personal liberty is compatible with the general good, and of the propriety of social conduct in all cases, is a matter of great extent, and demands the united wisdom of a whole people. And the consent of the whole people, as far as it can be obtained, is indispensably necessary to every law, by which the whole people are to be bound; else the whole people are enslaved to the one, or the few, who frame the laws for them.

Oscar Iden Lecture Series, Lecture 3: "The State of Individuals" (1976)

Vol. 1, Notes to the Chapters: Ch. 7, Note 4
The Open Society and Its Enemies (1945)
Context: The so-called paradox of freedom is the argument that freedom in the sense of absence of any constraining control must lead to very great restraint, since it makes the bully free to enslave the meek. The idea is, in a slightly different form, and with very different tendency, clearly expressed in Plato.
Less well known is the paradox of tolerance: Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them. — In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be unwise. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law, and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.

International Liberal Conference (July 1928)
Later life

Speech at the Charleston Bar Dinner (May 10, 1847); reported in Edward Everett, ed., The Works of Daniel Webster (1851), Vol. II, p. 393

Obergefell v. Hodges http://www.supremecourt.gov/opinions/14pdf/14-556_3204.pdf (26 June 2015).
2010s
Context: The Court's decision today is at odds not only with the constitution, but with the principles upon which our Nation was built. Since well before 1787, liberty has been understood as freedom from government action, not entitlement to government benefits. The framers created our constitution to preserve that understanding of liberty. Yet the majority invokes our Constitution in the name of a 'liberty' that the framers would not have recognized, to the detriment of the liberty they sought to protect. Along the way, it rejects the idea—captured in our Declaration of Independence—that human dignity is innate and suggests instead that it comes from the Government. This distortion of our Constitution not only ignores the text, it inverts the relationship between the individual and the state in our Republic. I cannot agree with it.