If your service is accessing the same data source (i.e. a data table) you have to filter the returned data yourself. That means getting the user group of the user who executed the service via "let groups = Resources["CurrentSessionInfo"].GetCurrentUserGroups();" and filter the data accordingly.
If your data is stored in different entities for each solution, you can just restrict the visibility to the data entities. But then you have to catch the exception that will be thrown, if your service is trying to access data sources to which the user does not have visibility rights.
