The Home Secretary can exclude or deport an individual if she thinks that their presence in the UK is not conducive to the public good.
There had been speculation that Dr Naik would be allowed into the UK. However Mrs May said she was excluding him because of the “numerous comments” he made were evidence of his “unacceptable behaviour”.
This behaviour applies to anyone who writes or publishes material which can “foment justify or glorify terrorist violence” or “seek to provoke others to terrorist acts”.
Mrs May told The Daily Telegraph: “I have excluded Dr Naik from the UK. Numerous comments made by Dr Naik are evidence to me of his unacceptable behaviour.
“Coming to the UK is a privilege not a right and I am not wiling to allow those who might not be conducive to the public good to enter the UK.
“Exclusion powers are very serious and no decision is taken lightly or as a method of stopping open debate on issues.”
Home secretary Theresa May bans radical preacher Zakir Naik from entering UK - Telegraph