As long as you are a student at a school you can practice as a walkon. They both are probably taking either grad or undergrad classes. Richardson is also a free agent at the moment so he is not in the NFL. I agree them practicing with the team is crazy.
Go Canes
Not that I don't believe you, but how does not being currently on a team matter? Isn't the ncaa's thing that once you've taken money you are a professional?
That's not the rule at all...
14.2.1.6 Exception—Former Student Participating in Practice on an Occasional Basis. A former student at the certifying institution (e.g., former student-athlete) may participate in an organized practice session on an occasional basis, provided the institution does not publicize the participation of the former student at any time before the practice session. (Adopted: 3/3/11)
Miami allows this as well:
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