You will not be able to prevent that other business from filing a fictitious business name solely on the fact that it is the same name as your LLC. You may, however, be able to assert the rights of your business name as a trademark. This depends on several factors including the following: whether you do indeed own the trademark rights to your business name and whether the products and services offered by that other business are similar to those offered by your business. If you do indeed have the right to protect your business name as a trademark, I would then recommend that you send them a cease and desist letter. In this letter, you would inform them that they are infringing on your trademark and that you are demanding that they cease and desist use of your business name in order to avoid your filing a legal claim against them.

Of course, as mentioned above, the first step is to determine whether you do indeed have a right to assert under trademark laws. Feel free to contact me if you need any help determining whether you have such right.

One thing you can't do is challenge the fictitious business name filing. If the guy is using your LLC's name, rightly or wrongly, he still can, indeed must, file and publish it as a fictitious business name use.

Fictitious business name filings/publications are NOT intended to create exclusive rights to use a name. They do not in any way resemble or act as trademarking devices. Neither, for that matter, do LLC formations have any significant rights-establishing power or force.

Next, consider that the guy may be unaware of your LLC, and perhaps would immediately change his mind about this name, if he were aware of it.......so contact him and tell him about your LLC. After that, you could consider a cease-and-desist letter, but you should avoid making any threats of legal action unless you're pretty sure you have an enforceable right.

Such a right could arise under trademark law, possibly even under common-law rather than statutory trademark law if you haven't applied for a trademark. California has recently adopted the Model State Trademark Act, Business & Professions Code sections 14200 to 14212.

Keep in mind that rights to business names are generally protected in relation to the likelihood of consumer confusion and the possibility for harm or abuse. For example, calling a soft drink, or even milk, "Popa-Pola" is probably a trademark infringement. However, if there is a Joe's Bar and Grill in Redding, that's not going to prevent there being another in Bakersfield, and ABC Corporation can name its paint color "Purple Passion" without infringing XYZ, Inc's. trademark of "Purple Passion" for zinfandel. So even if your LLC name were trademarked, someone a suitable distance away could probably use it, or someone nearby could use it for an entirely different product, without infringing. (The rules are stricter for very famous names such as Coca-Cola).