Defence Secretary Philip Hammond told ITV News it was not for him to judge whether Sgt Danny Nightingale should have been sent to prison.
He added that the Court of Appeal "acted swiftly" in this case which showed the system was "robust".
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The singer had been tweeting in support of migrants when she was bombarded with abusive messages.
Ministers are reportedly considering plans in a bid to lower inward migration.
In a tweet on Saturday, the US president didn't give a reason for his absence but said he wished"everyone well and have a great evening".