Different contributor here -- with a different answer.
1. Based upon your question, the location of your property is in Illinois. If so, then the Florida case law cited by the other contributor is generally inapplicable to your circumstances, because Illinois law is different.
2. Under Illinois law, slander of title is a false and malicious publication, oral or written, of words which disparage a person's title to property resulting in special damages. (Midwest Glass Co. v. Stanford Development Co. (1975), 34 Ill. App.3d 130, 339 N.E.2d 274; Home Investments Fund v. Robertson (1973), 10 Ill. App.3d 840, 295 N.E.2d 85; Restatement (Second) of Torts § 624 (1977).). The homeowners association is not slandering your title to property, because there is no claim that you are not the rightful owner. Rather the association is allegedly engaged in "trade libel" and/or "interference with prospective advantage."
3. A writing, to be [trade libel] per se, must contain a false statement which imputes to the plaintiff any of the following offensive categories: (1) the commission of a crime; (2) the infection with a loathesome disease; (3) the unfitness or want of integrity in performing the duties of an office or employment; or (4) words which adversely reflect on a particular party's abilities in his business, trade or profession. Bontkowski v. Chicago Sun-Times; Whitby v. Associates Discount Corp. (1965), 59 Ill. App.2d 337, 207 N.E.2d 482. This cause of action against the association is straightforward, because your business interests are being injured by the association's alleged contact with local real estate agents.
4. The elements of the tort of interference with prospective advantage require that the plaintiff must have a reasonable expectancy of entering a valid business relationship, and defendant must purposely interfere and defeat this legitimate expectancy, thereby causing harm to the plaintiff. (Tom Olesker's Exciting World of Fashion, Inc. v. Dun & Bradstreet, Inc. (1973), 16 Ill. App.3d 709, 713-14, 306 N.E.2d 549. This cause of action is also straightforward, based upon your facts, as the association is allegedly interfering with your ability to market the property for sale.
5. Based upon the above, you would appear to have a very credible legal action against the association. It's quite possible that a firmly worded cease and desist letter from a local attorney could stop the association's conduct. And, if not, then a civil action for the above-described torts seems quite credible to me. If I practiced in Illinois, I'd take the case.
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