You're granting an employee a special status that doesn't exist. Imagine a random person working to undermine a contract between the government and a business, motivated by an effort to obstruct law enforcement from enforcing the law. I'm sure you'd agree that this would obviously be illegal - that doesn't change simply because the person happens to be working for the business in question.
And no I don't think it's illegal. You seem deeply confused, where is the "obstruction"? If there is obstruction there should be a specific court order and the parties involved, otherwise it's just business. Do you think say, telling a amazon delivery driver who's asking for the location of some address a bs route is illegal?
It's still not clear to me, where did I anywhere imply it's any different if a single individual or company is in question. I said it's a matter between the company and the employee because a company may dislike the employees actions and choose to deal with it eg by firing them, the contracting party isn't involved here. It still seems to me at most a matter of contract whether it's directly a single person being contracted or a person as part of a company.
If it's still not clear, I am saying my understanding is unless it is very specifically part of an investigation and involves the party in question, the entity whether an individual or a company is irrelevant, they are just as far as it seems to me engaging in a business deal.