There are probably two ways to do it: the easy way and the hard way.
The easy way would be to take note of what happened and say that it won't happen again. When I look at recent lieutenant-governor appointments in the provinces, such as in Ontario and Quebec, I get the sense that the federal government has indeed taken note of this case. In Ontario, for example, the government appointed a Franco-Ontarian. We can therefore assume it won't happen again, given the uproar it caused. We have to keep hammering away at this issue.
The hard way would be to change the legislation and make things clearer. I believe the case is before the courts, so we await clarification. It would be a matter of stating explicitly that, as is the case for Supreme Court judges, governors general and lieutenant-governors will have to speak both French and English. We don't want to get to that point, but sometimes, when the government isn't doing anything, that may be the only way to spur it to take action.