“Adultery can be legal grounds for divorce.”
Yeah, but in Virginia I almost have to have an eyewitness to the copulation to prove adultery. Apparently the fact that they have been living together for the past 1.5 years is not enough proof.
And then there is the Clinton argument that certain types of sex is not sex.
Maybe you can get them to commit perjury and claim that they are not (in front of a judge and in a court).