Can you remove them out of your Sim's personal inventory by the hand grabber? - Mouse over item and grab, then pull to the sell box? or maybe to the ground?
If you're able to pull them out of the Sims personal inventory, try Deleting the object? - This needs to be done with testingcheatsenabled on. Shift-click on object and select Delete it.
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Forgive the example I don't have anyone that's a magician, so I grabbed a few things to put in my Sims inventory.
If you have Nraas MasterController installed you can use it to delete things out of your Sims Inventory.
Click an empty spot on your home lot > Nraas > MasterController > Object Stats > Inventory.
Click the items you want deleted and select the check mark to accept.