No I meant the sisters Vandene and Adeleas, specifcally - I'm rubbish with names so I had to look them up. From The Path of Daggers,
Here we can see that it is the laws of the Tower that are specific in deciding what constitutes a weapon or the limitations of use of the Power. This text also makes it difficult to see how Elaida could use the Power to punish Egwene, at least without breaking the law. But it is clear that Sisters can put people to the Question, with Power-fueled violence that is far more limited by in its scope by Tower law than the Three Oaths. It seems fairly clear to me that questioning and punishing, in the terms of the Aes Sedai, don't constitute weapons. It is entirely consistent that a legal execution would also not come under this category. "Use as a weapon" is a phrase that is nearly meaningless without context.
It is like the Roman concept of violence. Caesar's last words were reportedly "What is this? Violence against Caesar?" (not "Et tu, Brutus?"). Caesar was indignant as though Roman society was to our language inherently violent - to the Romans, such things as gladiatorial games, warfare, executions, etc., were not violence, they were morally and socially sanctioned actions. Illegally stabbing someone in Rome (where all weapons were banned, except for the Praetorians) was a shocking and, moreover, rude act Caesar considered himself above.