It seems Jay-Z is not willing to look past the fact that Rihanna has given Chris Brown, the man who violently beat her, a second chance.  There have been rumors floating around that Jay-Z and Beyonce do not wish to have Rihanna interacting with their daughter Blue Ivy, now that she has rebuilt her once crumbled bridge with Chris Brown.  Those close to the situation have said that neither Jay or Beyonce will not let her see Blue Ivy, so long as she chooses to have a relationship - romantic or otherwise - with Chris Brown.

According to an unnamed friend:

"Jay-Z's not only Rihanna's mentor, he's also like her big brother.  He got Beyoncé to tell Rihanna he doesn't want her around the baby if she takes Chris back.  He wants Blue to have positive role models, not someone who'd take back a man who hit her."

Source: hiphopblog.com