You have to satisfy the criteria of labor law, which is (working from memory here) that two or more employees come together in concert around a workplace issue.

You have to satisfy the criteria of labor law, which is (working from memory here) that two or more employees come together in concert around a workplace issue. At that point they are engaged in protected concerted activity and you can't just fire them. I don't believe the code review meets this test, but I'd love to hear from someone who knows what they're talking about.