“If the Soviet Government orders me to act against my conscience, I do not obey. As for teaching the Catechism, the Catholic Church holds that children must be taught their religion, no matter what the law says. Conscience is above the law. No law which is against the conscience can bind.”

The Kingdom of God is Within You (1894)

Quoted in "Words of Wisdom‎" - by Mick Farren - Philosophy - 2004 - Page 122
2000s, 2004

Maxim 237
Sentences, The Moral Sayings of Publius Syrus, a Roman Slave

Call for Reckoning http://pewforum.org/deathpenalty/resources/transcript3.php3 - Pew Forum conference (25 January 2002). N.b. this speech was later modified into an article - God's Justice and Ours http://www.firstthings.com/article/2007/01/gods-justice-and-ours-32 which repeats much the same points.
2000s

De Re Publica [Of The Republic], Book III Section 22; as translated by Francis Barham
Variant translations:
True law is right reason in agreement with nature; it is of universal application, unchanging and everlasting; it summons to duty by its commands, and averts from wrongdoing by its prohibitions. And it does not lay its commands or prohibitions upon good men in vain, though neither have any effect on the wicked. It is a sin to try to alter this law, nor is it allowable to attempt to repeal any part of it, and it is impossible to abolish it entirely. We cannot be freed from its obligations by senate or people, and we need not look outside ourselves for an expounder or interpreter of it. And there will not be different laws at Rome and at Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and all times, and there will be one master and ruler, that is, God, over us all, for he is the author of this law, its promulgator, and its enforcing judge. Whoever is disobedient is fleeing from himself and denying his human nature, and by reason of this very fact he will suffer the worst penalties, even if he escapes what is commonly considered punishment.
As translated by Clinton W. Keyes (1928)<!-- ; in De Re Publica, De Legibus (1943), p. 211 -->
Context: There is a true law, a right reason, conformable to nature, universal, unchangeable, eternal, whose commands urge us to duty, and whose prohibitions restrain us from evil. Whether it enjoins or forbids, the good respect its injunctions, and the wicked treat them with indifference. This law cannot be contradicted by any other law, and is not liable either to derogation or abrogation. Neither the senate nor the people can give us any dispensation for not obeying this universal law of justice. It needs no other expositor and interpreter than our own conscience. It is not one thing at Rome and another at Athens; one thing to–day and another to–morrow; but in all times and nations this universal law must for ever reign, eternal and imperishable. It is the sovereign master and emperor of all beings. God himself is its author,—its promulgator,—its enforcer. He who obeys it not, flies from himself, and does violence to the very nature of man. For his crime he must endure the severest penalties hereafter, even if he avoid the usual misfortunes of the present life.

1940s–present, A Mencken Chrestomathy (1949)

Book I, Ch. 22. Of Custom
Essais (1595), Bartlett's Familiar Quotations, 10th ed. (1919)

The trial of Charles B. Reynolds for blasphemy (1887)
Context: There is a constitution higher than any statute. There is a law higher than any constitution. It is the law of the human conscience, and no man who is a man will defile and pollute his conscience at the bidding of any legislature. Above all things, one should maintain his self-respect, and there is but one way to do that, and that is to live in accordance with your highest ideal.