Heron transferred from Auburn to St. John's in the spring, and the school applied for a hardship waiver so Heron wouldn't have to sit out a year before playing. A Connecticut native, Heron left Auburn to be closer to home. His mother has had medical complications since suffering a severe concussion, sources told ESPN.
"I'm incredibly thankful that the NCAA has decided to allow me to play right away closer to home," Heron said in a statement. "I would like to thank all of the staff at St. John's that fought to make this a possibility for me and my family."
Chris Mullin and the Red Storm now have one of the best backcourts in college basketball, with Heron playing alongside Shamorie Ponds. Heron, a 6-foot-5 shooting guard, averaged 16.4 points and 5.3 rebounds last season, helping lead Auburn to an SEC title.
Ponds is the preseason front-runner for Big East Player of the Year after averaging 21.6 points and 4.7 assists last season for St. John's.
"It is important for Mustapha to be close to his family during this difficult time, so providing him the opportunity to play immediately will be a great benefit as he continues to pursue his personal goals," Mullin said. "Mustapha is a high-character young man with loads of talent who will now be able to showcase it on the highest stage."
With Heron officially in the fold, the Red Storm will have NCAA tournament expectations despite finishing 16-17 last season. Mullin also returns Justin Simon and Marvin Clark, and welcomes fellow transfers Mikey Dixon, Sedee Keita and LJ Figueroa.