A Clark County Superior Court judge ruled this week that Vancouver lawyer Greg Ferguson cannot represent former Vancouver Police Officer Chris Kershaw in his wrongful termination case against the city, saying that Ferguson violated rules against representing clients with conflicting interests.Judge Barbara D. Johnson on Tuesday upheld a motion by the city to dismiss Ferguson as Kershaw’s attorney. Kershaw is in the middle of a wrongful termination lawsuit against the city, Assistant Police Chief Nannette Kistler and City Attorney Ted Gathe.In a motion filed in January, lawyers for the city had argued that because Ferguson represents both Kershaw and VPD Sgt. Dave Henderson, Kershaw’s former supervisor, he cannot represent either without damaging the other’s case.Henderson has filed a tort claim, noting an intent to sue the city. Both Kershaw and Henderson say they have been targeted for termination or discipline for speaking up on behalf of former Officer Navin Sharma, who won a $1.65 million wrongful termination settlement from the city in 2008. Ferguson was co-counsel in that case.Testimony in conflict?Seattle lawyer Mike Patterson, who represents the city, said that Ferguson can’t interview one man as a witness without compromising the credibility of the other, which is a violation of ethical rules.