The Creative Workers Union of South Africa said using foreign actors to tell the country's stories undermined efforts to develop the national film industry, AFP reports.
At a heated press briefing in Johannesburg on Saturday, the union and a group of actors said local and international producers must follow the right consultation procedures before "bypassing" the law and bringing international work and actors to South Africa, The Citizen reported.
"It can't happen that we want to develop our own Hollywood and yet bring in imports," the union's president Mabutho Sithole said, according to The Citizen.
The union said it would push for a meeting with the departments of arts and culture and trade and industry as well as home affairs.
Union secretary general Oupa Lebogo said in local newspaper The Times, "This decision must be reversed, it must be stopped now. If the matter doesn't come up for discussion, we will push for a moratorium to be placed on the film being cast in South Africa. We are being undermined; there is no respect at all."
Hudson, an Oscar winner for Dreamgirls, was cast in the role last month.
Morgan Freeman plays the president and Matt Damon is the rugby team captain, although no references were made to that film and its American actors in the round of union comments cited in articles about the Hudson upset this weekend.