If Kinsella were to go on a binge, he would drink his way down to the last penny of whatever money is available, irrespective of who it belongs to. (The killing frost. Thomas Hayden, 1991)
I think here "regardless of" can be used in place of "irrespective of". It seems "regardless of" covers all the meaning of "irrespective of", but not vice versa.For instance, I think in the following sentence, "regardless of" can not be replaced by "irrespective of":
In the future people will be selected for posts on merit, regardless of gender or race.
What do you think?