Protecting the Special Counsel.
Some Republicans try to make the case that "really it can't be done"; this stance relies (largely not exclusively) on a dissenting opinion by Scalia in a different case.
The problems with this view are many, but the clearest is, dissenting opinions are not law.
Even if the dissent was not flawed (which it is) it does not have the weight of a decision.
A nice discussion of the problems:

https://slate.com/news-and-politics/...-mistakes.html