Unfortunately, when you use a past employer as a reference, you are impliedly giving them permission to provide truthful information about you to prospective employers. If your former employer truly considers you not rehireable, they have the right to state that to an employer who asks that question.
You can contact the former employer and ask that they limit the information they give to simply verifying your dates of employment and position held. If the person you speak to refuses to comply, take it to a higher level. Hopefully, someone with sense will agree to limit your information.
