Media lawyer Paul Gilbert has told Daybreak that judges will have to decide on "whether or not a tweet itself is more than shocking or offensive."
He added: "It's finding a balance between what the law says about this and the freedom of speech."
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Sheridan Smith won a standing ovation as she returned to the West End stage after claims she was 'drunk' during a performance.
The 'Let Our Kids Be Kids' campaign wants parents to keep their children off school saying they are "over-tested and over-worked".
Nicky Morgan is expected to defend the proposal when she fields questions at the National Association of Head Teachers' annual conference.