Yes! Although consent by a parent, once given, is a defence in Hague Convention proceedings for the return of abducted minors, and cannot be retracted, this only holds if the consent is real, freely given, clear and unconditional. The parent claiming consent as a defence to the child abduction proceedings has the burden of proving that the consent was valid.
Consent obtained by trickery or under duress is not true and valid consent. If the father brings Hague Convention proceedings, for the return of children allegedly retained in Israel against his will, and can prove that the alleged consent was not valid, or was conditional, or limited in time, then he has a chance of his children being ordered home.
The Israeli court hearing the case will have to decide, on the basis of the pleadings and evidence,both written and oral, including the actual wording of the note itself, the circumstances and conditions under which it was made, and from cross examination of the parties and witnesses on the subject, whether the father really ‘consented’ to his children remaining in Israel or not. If it decides that his consent was valid, then, the court has discretion not to order a prompt return of the minors. If , however, the court decides that the consent was not valid, then it will be under an obligation to order the children home promptly, unless there are other grounds for a valid defence.
Another possible defence, related to consent, is ”acquiescence” (retroactive consent). Again, the burden of proof lies with the person defending the child abduction proceedings.