From a legal perspective, I'm not sure that it matters whether the work was done by a contractor or employee. Whoever asked for the work to be done and paid for

From a legal perspective, I'm not sure that it matters whether the work was done by a contractor or employee. Whoever asked for the work to be done and paid for it is ultimately responsible for ensuring that it was done within the law. Certainly MS would be able to turn around and sue the contractor, but that's a separate issue.