According to MLK we can tell the difference between just and unjust laws because just laws uplift human personality and unjust law is a human law that is not rooted in eternal law and natural law.
I do not think this is a valid or important distinction between just and unjust laws. I say that because sometimes how humans behave naturally is not the best for society. So laws are needed to correct these natural laws humans would live by for the better good of everybody. I do think it makes a difference in the way someone or our society lives. It affects them because most people do not want to stand out so they will follow laws whether they are just or unjust. It differently can affect our politics because politicians can manipulate the citizens of the society to learn towards certain ideologies which in return help shape how certain laws are viewed.
An unjust law using MLK’s definition would be the ability to by and or produce military grade firearms. It is clear that most Americans are against it and it causes great harm to our society. A just law would be the acceptance of gay marriage in America. This is just because it uplifts the people who it directly affects but also uplifts the people around those individuals. It has a trickle affect that makes everyone’s life easier and uplifting.