The TV chef was not allowed to board a British Airways flight from London’s Heathrow airport to Los Angeles.
At the weekend, 54-year-old Lawson was barred from boarding a flight to America.
An eyewitness told the Daily Mail Lawson had tried to board the British Airways flight from Heathrow's Terminal 5 to Los Angeles on Sunday morning but was turned away.
"She didn't seem to say much but she did not look happy," they said.
"She could not get on the flight so she had to turn around and leave."
Lawson admitted she had taken cocaine and cannabis during the trial of her two former personal assistants last year.
Luke Macgregor / Reuters / Reuters
Scotland Yard decided not to take action over her confession, but the US authorities now appear to have taken a tougher stance.
The 54-year-old is a judge on the US talent show The Taste and it remains unclear how the alleged events of the weekend may impact on her TV career.
The US Department of Homeland Security said it did not comment on individual cases.
However, a spokesman is quoted by the Mail as saying foreigners who had admitted committing drugs offences in the US or another country were deemed to be “inadmissible”.
(Photo: Andrew Matthews/PA)
In general, an alien found inadmissible will need a waiver of inadmissibility.
Depending on the basis of their refusal they may be eligible to apply in advance of travel for a temporary waiver of inadmissibility. The waiver application process can be lengthy.
