A former employer is only allowed to make truthful and factual statements about former employees. So if an employee was fired for stealing, for example, there would be nothing that employee could do legally to prevent the former employer from stating this to potential employers.
Employers cannot make value judgments, like "employee was lazy" or things that are not true.
Most employers avoid as much as possible for fear of a lawsuit, but it doesn't sound like your former employer is doing that. So the first and most obvious question is "How do you know they are saying bad things?" and then the next question is "Are they saying things that are not true?"
If they are saying things that are not true, then your remedy would be to sue the former employer for defamation of character. Usually, a cease and desist letter from a lawyer will get the job done. You can hire a lawyer to write you a letter threatening the employer at a pretty small cost. This is often effective even if the employer is acting lawfully.
Thanks for your help.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).