When the divorce command is used, a divorce arbour will be created and the ceremony may commence.
Both parties must accept the divorce before it can be completed, and the divorce can only take place at the divorce arbour.
There is also a time passage requirement between marriage and divorce with this command. If you try to perform the ceremony too soon you will see a message like:
The honeymoon isn't even over yet, Frog and Womble cannot divorce right now.
After testing this a bit we currently believe that it is either 14 RW days, or 40 DW days.
Syntax for the officiant:
divorce <living> from <living>
complete [the] divorce
Syntax for the couple: