By the CBA, DeAngelo cannot return to Carolina within a year of his trade from the Canes, especially when salary is retained. The two teams are set to discuss with the league in Nashville, who could either sign off on the trade or force both teams to wait until July 9th.
It's unclear whether the trade will still go through if the Flyers and the Canes are forced to wait.
I am not super knowledgeable about this side of thing - but it seems like the teams' argument is that the Flyers signed DeAngelo a year ago and not the Canes, so this clause technically shouldn't apply. Letter of the law vs the spirit of it.
We'll see what the league says. I would imagine that if the trade is put on hold, plans would change after the free agent market opens, and this doesn't end up happening.