Executive power 2000 years ago

[Ismq]

There is a question that I've been asking myself for a long time. I hesitated to ask it here, because some of you could feel attacked since some Christians accuse Jews to be responsible for the death of Jesus. But I don't see it that way (I believe that it was His mission to come and die. So someone had to do it).

Here is my question: In the times of Jesus the people of Israel weren't allowed to kill (John 18:31) and therefore Jesus was handed over to the Romans. A little later, when Stephen appeared on the screen, the people stoned him. (Acts 7:58-60).  What do you think, why was it not allowed in one case and allowed in the other?

You can find informations about that in biblical commentaries.