Nigella Lawson's admission of using cocaine has resulted in her being barred from entry into this country. I think that this is absurd and opens up the policy behind it for ridicule.
The list of people who have admitted doing cocaine and/or worse is too long to even begin to contemplate. There is no reason whatsoever for this country to admit the likes of Eric Clapton or Keith Richards and yet, it would be unthinkable for U.S. authorities in this day and age to deny them entry to the United States.
Policies like this hit people in the arts and entertainment field pretty hard. But they are rarely applied in a fair and uniform manner. Lawson may exist in that realm between reality television and non-fiction television where a specific set of professional skills are displayed, but she does not deserve to be barred from entry just because of an admitted use of drugs.
Now, if she shows up at the border looking like she smashed a powdered doughnut into her nose and carrying an Archer amount of cocaine, yeah, you could bar her.