The Daily Express says Campbell has been told he must agree to a five-year "gagging order" by Notts County before they let him continue his career.
County are refusing to release Campbell's registration and he is calling on players' union chief Gordon Taylor to intervene on his behalf.
Campbell wants to go public on certain aspects of his time at County, which ended after only one game - a defeat at Morecambe. County want him to keep quiet before a "statement of departure" is agreed.
Taylor said: "Clearly, Sol needs to express the real reasons behind his departure, and will not agree to a gagging order. Instead, we are trying to agree a form of words, a statement both sides are prepared to accept."