The other aspect is that, I don`t know so this is a wild assumption, a Special Advisor would also be an employee?
If that is the case then his behaviour falls way, way short of anything near Gross Misconduct - especially in the public sector where it is nigh on impossible to get sacked.
So, if he has admitted his transgression to his boss and received a verbal or, at a push, a written warning that is it.
And the matter would remain confidential under the same employment legislation and public sector policies and procedures.