Matthew's example is a bit nicer though, because in my example W eventually has to capture the stones. It is Black's move. The superko rule is in use. Common sense, and all other rulesets, suggest that White's upper group is alive. White plays 'a', capturing two stones.
Black plays 'd' in the lower left corner, as a ko threat.
White answers at 'c'. White cannot play with putting himself in atari, and so passes. Black plays 'b' and says atari. He reminds White that a play at 'a' will repeat a previous position. Many Thanks to Fred Hansen of the Andrew Consortium for yet again producing the gifs which he created from files consisting of X's and O's, using their tools.