According to reports, the celebrity chef, 54, was stopped from boarding a British Airways flight from London to Los Angeles last Sunday.
While a rep for Lawson would not comment on the situation, Britain's Daily Mail reports that one reason for her denied entry could stem from her explosive testimony during a fraud trial against two former personal assistants in December, during which Lawson admitted to having used cocaine and cannabis in the past.
Britain never pursued legal action against her over those revelations. But under U.S. law, foreigners can be denied entry for drug offenses even if they have not been charged.
When asked if her previous drug admissions affected Lawson's travel plans – even though she has no previous convictions – a U.S. Embassy spokesperson told PEOPLE, "This is what I can't get into. I can say that we don't see this as barring travel to the U.S."
But before doing so, the U.S. Embassy requires The Taste judge to apply for a new visa.
"Ms. Lawson has been invited to come and apply for a visa," the spokesperson said. "We understand that she has professional requirements for travel into the U.S. We handle these matters routinely and expeditiously. I don't think that this is something that drags on and on."
British Airways declined to comment on the situation. But Anthony Bourdain, her outspoken costar on The Food Network and ABC's reality cooking competition The Taste, weighed in on Twitter:
I am absolutely mortified with embarrassment over the cruelty and hypocrisy of US actions re: #Nigella travel. Unbelievable.— Anthony Bourdain (@Bourdain) April 3, 2014
A day before the incident, Lawson posted a note on Twitter saying she was packing for a vacation, along with a photo of a sun hat and a small tube of Colman's mustard.
Later, she apparently shuffled her travel plans. "Off line for a while enjoying the ultimate; a holiday break with no signal!" she wrote on Monday. "Will miss you all though. Know I will be eating on your behalf."
Additional reporting by MONIQUE JESSEN