Question

Martin luther king jr.'s letter from a birmingham jail argued that people have a moral responsibility to obey just laws and:

Answer 1

I would say that King probably said that people have a moral right to obey just laws just as they have that same moral right to disobey unjust laws such as the laws of segregation between whites and black Americans in some southern states.

Answer 2

He wrote that when the laws are not truly true to what they are meant to do, then insubordination and civil disobedience is justified   
His writing the letter was inspired an announcement made by eight white Alabama ministers a couple of days earlier , titled "A Call For Unity,". He conveyed in his letter that though social shameful acts were occurring yet communicated the conviction that the fight against racial isolation ought to be battled exclusively in the courts and not taken onto the roads.