Veracity of Carte Blanche in The Three Muskateers

In the book The Three Muskateers a character is given a note from the Cardinal Duke saying that >By My word and for the good of the state, The bearer has done what has been done. Was the Cardinal [who did exist](http://en.m.wikipedia.org/wiki/Cardinal_Richelieu) able to do this as the Highest religious official in the country, or as a person in great power during a time of war? Or is this just a total fabrication of Dumas, with respect to princes secular or religious? If not, this doesn't also qualify as absolution does it?