Yes - MS is an at-will state. But, many times, the better question is whether the employee can point to some exception to the at-will rule such as anemployment contract, handbook provision, promise of continued employment, etc. to show that he/she was not at-will. This includes any progressive discipline provision in a handbook that does not allow for an "escape" of termination at the employer's discretion at any point in the process. The employee may also point to a public policy exception to at-will (such as whistle blower protection, retaliation for exercising some legally protected right).
If the employee is a member of a protected class (remember age too), he may also believe that he is additionally protected (and he may be).
You terninated the person for insubordination. In my company this would be a policy violation and that is the reason that I would terminate the person. I would assume that you had your documentation in order before you did this. HRDir1 does bring up a good point about the discipline provison in your handbook. Hopefully you followed the process you have or you have the clause that allows you to deviate from this process based on the nature of this incident. It sounds like the person is just trying to throw something out there to see what happens.
Because you were not sure if MS was an at-will state I would do the following: You need to look at a bunch of documents to make sure that it is clearly marked with the at-will clause. Make sure your offer letter talks about at-will. Your handbook should talk mention at-will on several different occassions, in bold print and underlined. Your disciplinary policy should be written so that if you want to have certain steps (i.e. verbal warning, written warning, final written warning and termination) that the company reserves the right to change/alter and or skip over steps depending on the nature of the situation. My employees know that my state is an at-will state based on the documents that I have given them.
All of our documentation - offer letters, handbook, policies - clearly state at-will. We have no progressive discipline policy. We recently acquired this company, and so have never had an office in MS. This is the first time anyone has ever said anything regarding at-will, and so I thought it was worth investigating even if he's just throwing anything and everything at us to rattle our HR Rep.
Thanks for your help.
efeldman - it is always better to be prepared!
Here is a good link I found. It has other links that may interest you, especially since you are not used to doing business in that state.
Every state in the union is an at-will state with the surprising exception of Montana, which recently enacted a for-cause termination requirement.
The only difference between the other 49 states is the extent to which you have to worry about whether or not your termination decision will be scrutinized for illegality and the burden of proof required to prevail under such scrutiny. California, known for it's litigiousness and administrative burdens, is about as hard as it gets. Business friendly Texas, in the business friendly no-nonsense 5th circuit, is about as easy as it gets.