From time to time one is presented with adhesion contracts which have not been signed by the presenting party, and contain terms which are unpalatable.
Were one to modify the contract in ways which may not be picked up by the other party prior to signing it to make it more equitable/favourable to oneself prior to returning the document, and without drawing the other parties attention to the changes, would one be acting illegally ?
I'd be interested in any specific laws which might cover this for a particular jurisdiction, but I'm more interested in any underlying basis in law why this behaviour would be considered illegal. (One thought is breach of copyright, but I'm not sure if that could be applied)