It could be that the attorney is saying that they are renewing the judgment. If so, then, then that is allowed--that is, in California, a judgment creditor may renew a previously entered judgment every 10 years.
A California judgment is valid for 10 years and can be renewed for another ten years.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Do not listen to any legal threats made by a debt collector.
A few questions. Was there a money judgment entered as part of an unlawful detainer action was there a separate lawsuit later? If so, was thee a default judgment entered? A default judgment might be invalid if there was not proper service of process. It will be necessary to review the court documents.
They can renew the judgment in California if they do so within 10 years after entry of the original judgment. However, a California judgment cannot be automatically enforced in another state. The creditor would then need to file an action in Illinois. You might be able to contest the validity of the California judgment if the California court never acquired personal jurisdiction. The Illinois proceeding would need to be filed by an Illinois lawyer. There would also be a court filing fee involved.
Illinois has exemption statutes. I am not familiar with Illinois law specifically, but you may be able to exempt more than 75%, perhaps all, the judgment debtor's salary if it is necessary for the support of the debtor and his/her family. They probably cannot levy on gov't benefits, social security and many other types of assets.
So, the creditor is going to have to renew the judgment in California, and pay the California filing fee. Then, it will need to employ an Illinois lawyer and pay fees to the State of Illinois. Also, process serving fees. All in order to get a renewed judgment that they cannot collect. Their threats do not make business sense for them.
As to your credit, the account should be removed from your credit after 7 years. You can file a dispute with the credit reporting agencies. If they do not remove it, you may want to consult a lawyer who is experienced in suing for violations of the Fair Credit Reporting Act.