No it wasn't. How can you pardon someone without a final verdict?
Whatever the correct word for it be a reprieve, clemency, pardon, or whatnot, that is not important. What is important is that the Presidential pardon in Poland (as in the US) can be granted before or after conviction of the crime.
It has been tested in this case as the Constitutional Tribunal ruled in this very case that a presidential pardon can be granted before conviction of the crime and the same had been later ruled by the Highest Court.
So, we have The president and his interpretation and his pardon, which is supported by the ruling of the Constitutional Tribunal, and what stands against it? - some a bunch of political activists in togas that decided they were above the Constitution, the ruling of the CT, and the President. Wow!
In that case, I Ironside the mighty ruler of this Galaxy in my wisdom find them guilty and sentence them to hanging - I guess it is as legit as anything in your eyes? geez.