Well it could have been. The marriage only exists on paper anyway, a legal formality without any substance to it. But were it to be anulled, then Michael Schiavo would have no legal standing to kill Terri. And for whatever guilty reason, he seems very badly to want her dead.
can't be annuled becasue the marriage was not entered into under fraud, misrepresentation or duress.
In addition the evidence for no fault is "irreconcilable differences" He is not saying the differences are irreconcilable.
The only legal way for her to petition for divorce as an incapacitated person is to have her guardian petition for her. That is why the mother and father want to be the guardians.
I just though a little legal fill might be good FYI.