The issue you are describing is creating an "inadvertent MEWA." There are potential issues at both the federal and state level with respect to this arrangement. Often state law does not directly address this type of MEWA arrangement; therefore, further analysis and often discussion with the state DOI is required.
Depending upon the type of transaction that resulted in the sale, there are different options for continuing group health plans.
I agree with the commenters above that you should consult with an employee benefits attorney very soon to determine potential exposure, and explore the best option for your client.
