Well... Which is it, Luke?

Yes

"Master," said John, "we saw a man driving out demons in your name and we tried to stop him, because he is not one of us."
"Do not stop him," Jesus said, "for whoever is not against you is for you."
      -Luke 9: 49 - 50

or No

Some Jews who went around driving out evil spirits tried to invoke the name of the Lord Jesus over those who were demon-possessed.  They would say, " In the name of Jesus, whom Paul preaches, I command you to come out."  Seven sons of Sceva, a  Jewish chief priest were doing  this. One day the evil spirit answered  them, "Jesus I know, and I know about Paul, but who are you?"  then the man who had the evil spirit jumped on them and overpowered them all.  He gave them such a beating that they ran out of the house naked and bleeding."
-Acts 19: 13 - 16

Well, Luke?  Which is it?