The Metropolitan Police chief said a campaign launched to identify possible victims of female genital mutilation (FGM) "warns" people of the law.
Sir Bernard Hogan-Howe said: "They have an option to stop - the fact they bought a ticket to me is irrelevant.
"They should not be committing a serious attack on a child and they should not be breaking the law."
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Tony Blair could be made to stand trial for war crimes over the invasion of Iraq, Labour leadership frontrunner Jeremy Corbyn has said.
The number of fines handed out to hauliers found carrying illegal immigrants into the UK has more than tripled in the last three years.