[digitallyfree]

It depends on the contract - don't some universities have an IP clause (like many companies) where all work/research you perform there becomes the property of the university? They then give you limited rights to use this content for personal study, etc. This means that all work performed by the student for the purpose of the assignment is then under the university's copyright.

I suppose they could take this a step further by making students sign a confidentiality agreement for assignment solutions, which is legally stronger than a honor code agreement. I won't be surprised if this becomes a thing in the future.