Scripture
It is said that genuine believers have the ability to cast out demons, below is an example:
He that believeth and is baptized shall be saved; but he that believeth not shall be damned. And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.
And another example of a man driving out demons in Jesus' name being respected.
And John answered him, saying, Master, we saw one casting out devils in thy name, and he followeth not us: and we forbad him, because he followeth not us. 39 But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me. Mark 9:38,39
In the scripture below Jesus mentioned that even those who drive out demons can be condemned, how can it be?
Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name{LIE!!!} done many wonderful works?{LIE!!!} Matthew 7:22
Works folowed by a?
Have we not prophesied{preach} in thy name?
And in thy name have cast out devils?
There are many false teachers in this world today, they preach in vain and they preach to gain, taking tithes and offerings and being greedy of material gain. So in other words they preach without love but love only for themselves. Likewise with those who pretend to cast out demons.
Matthew 15:8 - This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me.
Demons can be casted out easily, if they have fear then they are overcomed because not trusting in the Lord, they{demons} are submissive to Jesus, and they have no authority over Christians because of the name.
1 John 4:18 - There is no fear in love; but perfect love casteth out fear: because fear hath torment. He that feareth is not made perfect in love.
God Bless!