Movie theatre chain AMC has apologized to a North Carolina civil rights leader after he was kicked out of a screening of The Color Purple for trying to use his own chair in the disabled section.

The Rev William Barber, a former president of the NAACP North Carolina chapter, who suffers from a form of arthritis known as ankylosing spondylitis and walks with two canes, said that he tried to use a special chair he brought to an AMC Cineplex in Greenville on Tuesday afternoon and was told by staff he couldn’t.

Barber, 60, later told CNN that he has a medical condition that makes it impossible to sit in a regular chair. Barber shared a video of the incident that showed a stool-type chair with a backrest and no arms. (Barber has written for the Guardian.)