When a law is just it is our duty to obey it, but when the law violates the life, liberty or property of another human being, it is our duty to refuse to obey it. Thanks to the courage of Rosa Parks blacks are no longer required by law to sit in the back of a bus.
Just because Congress passes a law, it does not guarantee that the law is just. Congress, the President and the Supreme Court supported the Fugitive Slave Law in the 1800's and they misinterpret the Constitution on a regular basis today.
We the people are the final arbiter or what is and what is not constitutional and we cast our vote by refusing to obey those laws that we feel are unjust and unconstitutional. The states have a right to nullify legislation that they consider unconstitutional.
Henry David Thoreau advocated that when the government exceeds its lawful authority, it is our duty to engage in acts of civil disobedience.
Unjust laws will disappear when a significant number of people refuse to comply with them. If we want a law to be changed refuse to obey the law. The principle of jury nullification allows members of a jury to determine the guilt or innocence of a defendant and the authority to determine the punishment.