One they have been ‘pardoned’ they are no longer ‘illegal’.....................
If they stay in the country they are still breaking the law, the law didn’t change with their pardon.
You cannot be pardoned for future crimes just past.
As soon as they are pardoned if they are still in the country they just broke the law again.
Now that’s not to say he won’t play on the ignorance of the illegals and try it, but the illegals would still be in the country illegally.