In his letter, penned from a jail in Birmingham, King addresses eight white clergymen who criticized King's efforts to bringing about much-needed change in Alabama. One of their criticisms lay in the fact that King and his followers broke some laws in an effort to accomplish their goals.

King responded that there is a difference in just and unjust laws and aligns himself with St. Augustine that "an unjust law is no law at all." A just law follows moral codes and the law of God. An unjust law does not follow moral codes. Just laws uplift the human spirit while unjust laws diminish the human spirit. Therefore, any laws upholding efforts of segregation are unjust because they seek to harm the soul of another person. King asserts that laws which give one group of people a false sense of superiority and another group a false sense of inferiority are unjust.

King's followers (and all of America, really, at that time) had to discern between two very conflicting sets of laws. On one hand, the Supreme Court decision of 1954 dictated that public school segregation was illegal and could not be further implemented. On the other hand, for nearly two decades thereafter, schools in various locations (even some in the North) continued to implement segregation in practice. Additionally, the remnants of segregationist practices in businesses around the country, particularly in the South, left many feeling that false sense of inferiority. King argues that when determining which law to follow and which to reject, one need only consider the basic morality of the law. In this case, the decision of the Supreme Court was the one upholding morality.

King goes on to say that when a majority inflicts laws on a minority who had no voice in the democratic process via elections and voting, those laws are also unjust. King points to numerous counties without a single registered African American voter even in places where African Americans constituted the majority of the population. This, he determines, cannot represent the views of a true democratic process.

King furthers his argument by pointing to the reason he was arrested and sat in jail penning this letter: parading without a permit. He states that since he was arrested in an effort to quieten his voice about desegregation under the guise of another law, then that law also becomes unjust in its application.

King's voice was of paramount importance in opening the eyes of the country to needed reform in laws that served to dehumanize many of its citizens.