Civil disobedience is certainly not a new notion, and there's a long tradition of times when history has shown it to be necessary and reasonable. The authors of the Declaration of Independence stated conditions under which they felt civil disobedience is justified.
"Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn that mankind are more disposed to suffer, while evils are sufferable than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same object, evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security." -- Declaration of Independence
References to other sources justifying civil disobedience are given at the end of this chapter.