New York City Mayor Michael Bloomberg’s ban on large-size sodas at certain establishments, colloquially known as the soda ban, is a lesson in how to make your cause look ridiculous.

Bloomberg hoped the ban would spark a nationwide crackdown on sugary beverages. Instead, it became the subject of widespread mockery, inspired an instant-classic New York Post headline (“Soda Jerk”) and got struck down by a New York judge this week as “arbitrary and capricious.”

You could say that Bloomberg jumped the shark, except shark-jumping is associated with undue health risks that may burden public hospitals in the vicinities where it takes place and therefore should be banned in all coastal areas of the United States.

If the makers of “Schoolhouse Rock!” were to illustrate the process whereby New York almost got its soda ban, it would be very easy. Mayor Bloomberg tells the New York City Department of Health and Mental Hygiene what to do, and it does it. No fuss or muss with the City Council, the elected body accountable to the people of New York that is supposed to write laws.

Bloomberg managed to craft a measure with the least possible bang for the diktat. It forbids drinks over 16 ounces at restaurants and delis, movie theaters and food carts. It doesn’t ban them at supermarkets or convenience stores, where people buy most of their soda. It leaves 7-Eleven and its unapologetically gut-busting Big Gulp unmolested.

In other words, the soda ban is like prohibiting cigarette advertising — except for Joe Camel and the Marlboro Man. Or like forcing top-shelf New York restaurants such as Per Se and La Grenouille to no longer serve bottles of wine as a way to fight alcoholism.

Bloomberg is a true believer in the lifesaving consequences of his health agenda, and his smoking ban did indeed sweep the country. Yet his soda measure is so obviously ineffectual symbolism that it has a whiff of imposing his will for the sheer sake of it.

The city’s lawyers argued in court that the Board of Health could hand down the new soda rule because it has broad powers to fight disease. But there is a difference between an outbreak of a deadly communicable disease that has people dropping in the streets and excessive soda consumption. If someone drinks a 32-ounce Cherry Coke next to you at a movie theater, it doesn’t make you sick.

In his decision striking down the ban — which the city is appealing — Judge Milton Tingling mentioned that, in the 19th century, the Board of Health was given the power to put contagious patients out to sea in floating hospitals. If a health expert from some university somewhere suggested floating obese people out to sea as a weight-loss measure, Bloomberg might be sorely tempted.

A mere partial ban on large serving sizes is unlikely to have any effect, though. In a piece for The Daily Beast, Trevor Butterworth noted a study that found the top-consuming 20 percent of adolescent boys drank an ungodly 193.6 ounces, or more than a gallon, a day. Does Bloomberg think anything he does short of an outright ban on all soda will stop these kids? Even in that event, they would undoubtedly visit Mountain Dew speak-easies and imbibe home-brewed Dr Pepper.

If the mayor somehow succeeded in reducing the calories people get through soda, they could always get them another way. In a study called “From Coke to Coors,” Cornell University researchers conducted an experiment “in a small American city where half of the households faced a 10 percent [soda] tax and half did not.” They report that “in beer-purchasing households, this tax led to increased purchases of beer.”

The New York Times related that the mayor’s office is particularly anxious over the fate of the soda ban because the mayor is more and more concerned about his legacy. He shouldn’t worry. His reputation as the nation’s foremost highhanded scold is already well-established.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.