FIFA's ruling, which came after the intervention of Donald Trump, permits Florin Balogun to play in the co-hosts' World Cup last 16 match with Belgium later on Monday.
The 29-year-old had an outstanding United Rugby Championship season and is one of seven Bulls in the starting line-up for Loftus Versfeld Stadium in Pretoria.
Summer McIntosh broke the world record in the 200m butterfly on Sunday at the Canadian Swim Championships in Montreal, shattering the oldest world mark in women's swimming.