Permission.

History The New York Times has an obituary for Amelia Boynton Robinson, who was a pivotal member of Martin Luthor King Jr's group.

"Mrs. Boynton Robinson was one of the organizers of the march, the first of three attempts by demonstrators in March 1965 to walk the 54 miles from Selma, Ala., to the capital, Montgomery, to demand the right to register to vote.

"As shown in “Selma,” the Oscar-nominated 2014 film directed by Ava DuVernay, Mrs. Boynton Robinson (played by Lorraine Toussaint) had helped persuade the Rev. Dr. Martin Luther King Jr., who would lead the second and third marches, to concentrate his efforts in that city."

There's one key moment in Selma which resonated with me while watching the film last night, when, during the second attempt to cross Edmund Pettus Bridge in Montgomery, MLK decides not to go. After a prayer, he turns the group, who've travelled from across country to support him, around and walks them back again. This Guardian archive collection describes it thus:

"In the aftermath of Bloody Sunday, King himself led a symbolic march across the bridge once again. While demonstrators were more determined than ever to proceed, federal protection was needed if they were to make it to Montgomery safely. Stopped by police, the marchers kneeled and prayed, then turned around and retreated back into Selma."

The King Encyclopedia has further details.  A key character and story point then becomes the question of why this happened, why Luther King made this choice something which I haven't been able to find an answer for.  It's not really explained in the film, other than that there were safety concerns and that King received a message from God.

But my understanding, my takeaway, is that King decided not to go, either consciously or otherwise, because he was effectively being given permission by the white folk.  As portrayed in the film, the police who at the first attempt in Bloody Sunday had beaten and tortured the marchers were stepping aside to let them through.

The only acceptable scenario King would have had for marching would have been if the road had been empty ahead anyway.  But then of course, if that had been the case, there wouldn't have been any reason to march in the first place.

The film doesn't make this explicit.

But as continues to be the case, in terms of both race and gender, the fight for equality and human rights remains a process of convincing those in power to give a permission there shouldn't be any question of them being in a position to decide to give in the first place.  They shouldn't even be in the way.