Members of the African Union met for a two-day summit on Monday, and much of the discussion centered on Donald Trump’s Muslim immigration ban. The executive order affects U.S.-bound travelers from Libya, Somalia and Sudan, all AU member countries. In particular, representatives of the Union’s 53 member states took issue with the ban’s historical hypocrisy. The Independent reports that South African politician Nkosazana Dlamini-Zuma noted that “The very country to which many of our people were taken as slaves during the transatlantic slave trade has now decided to ban refugees from some of our countries.”

The executive action, which also puts a block on travelers from four Middle Eastern countries—Syria, Iraq, Yemen and Iran—has been widely criticized both within and outside U.S. borders. Almost immediately after Trump signed the order Friday, protests erupted around the country, with thousands of demonstrators heading to airports to express outrage over the ban. A wave of demonstrations also took place in cities across the UK, from London to Glasgow. European leaders have also been critical of the ban.

Dlamini-Zuma cited the ban as “one of the greatest challenges” facing the AU and suggested that as Trump assumes the American presidency, the world is “entering very turbulent times." Above all, the anti-apartheid activist called on AU member states to prevent Trump’s order from sowing discord and disorder.

“What do we do about this?” Dlamini-Zuma asked of fellow AU member representatives. “Indeed, this is one of the greatest challenges to our unity and solidarity.”

Quartz writer Yomi Kazeem notes that Trump’s travel ban will likely impact travelers from African countries not explicitly targeted in the executive action. Kazeem points out that under Sections 8 and 9 of the order, “a number of African countries might be subject to reprisals of visa fee hikes and curtailed visa validity periods,” and will likely face lengthier processes for visa renewals.