An overnight story from Reuters reports that Jean-Jacques Jauffret, a French scriptwriter, is suing Air France after being forced to pay for a second seat on a flight from India last year.

Jauffret admits to weighing more than 160kg. Apparently the airline’s staff measured his waist at New Delhi airport and decided he was too big for a single seat. Air France’s lawyer told a French court that “the company had a clear policy of asking obese passengers to pay for two seats.”

According to the report, he said “Let’s be objective. This man is fat. … He barely fits on the courtroom chair. How could he sit in an aeroplane?” Jauffret said he “felt shocked and humiliated” at the remarks.

Cases like this expose some of the problems of anti-discrimination rules. There is general agreement that people should not be discriminated against on grounds that are irrelevant to the matter at hand. Relevance, however, is sometimes in the eye of the beholder.

Weight and its distribution are clearly matters of some importance for air travel. The smaller the plane, the more carefully luggage is restricted and passengers are placed so as to avoid imbalance. Yet commercial airlines invariably allocate luggage allowances regardless of the weight of the passenger: a 50kg passenger gets no credit for the fact that they are weighing down the plane less than a 100kg one.

Any airline that set up a system of differential fares or allowances would be, like Air France, at the mercy of attack for discrimination against the overweight. From the thin persons’ point of view, however, they are the ones being discriminated against.

Either policy involves “discrimination” – which after all just means “choice”. The issue is whether or not the grounds for discrimination are relevant, and that is simply not a matter of hard fact.

Like censorship, which depends on the government being exclusively able to determine the meaning of words, anti-discrimination law requires a sort of omnipotence that the law does not have. Barring extreme cases, the best option is to let people make their own choices – to discriminate on the grounds that seem relevant to them, and leave the courts out of it.