More information is needed to even take a guess on this. Whether a noncompete is enforceable or not usually depends on things like the length of time and the geographic restriction. Generally speaking, courts are less likely to enforce agreements that go on for a long time (over 1 year), cover a broad geographic region, or would prevent someone from earning a livelihood, particularly if they weren't very high up or very highly compensated. Since you've already received notice from your former employer to cease and desist, you really should find an employment lawyer in your area to review your noncompete and advise & assist you with a response.
Feel free to contact me if you want. Dan Knauth email@example.com // 212-317-1200. Answers to questions are meant to be general only, are not intended to be legal advice and do not create an attorney-client relationship. Answers to questions are based on NY law, and the laws of other states may create different rights and obligations.
The question as to whether a particular non-compete agreement can hold up (and to what extent) in New York State is a complex question with an answer full of probabilities along what is essentially a sliding scale.
Generally, New York State can be a little predisposed to be aggressive towards such agreements, but you to get any form of valuable answer on this question you need to sit down with an experienced employment attorney in your area and bring a copy of the agreement itself.
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Whether your non-compete agreement is enforceable under these circumstances depends on how it is worded, among other things. Just because your former employer is no longer in that business does not necessarily mean you're off the hook, as the agreement may apply to its successor, as well.
The information provided above is for general purposes only. It does not constitute legal advice or create an attorney-client relationship. Seek competent legal representation, because the facts of each case are different.