The other day the president was in Florida to extol a successful drug-busting operation. He fished from his memory the story of a California judge who threw a drug case out of court because a police warrant hadn't authorized the search of a baby in diapers.

These homely presidential anecdotes terrorize Reagan's White House staff because the facts, often as not, get mixed up. This time, however, he was right -- or almost right -- about the facts of the story if not about its significance.

In Colton, Calif., 13 years ago, police on a house search did find heroin cached in the diaper worn by the infant daughter of one Romona Padilla. A municipal judge did rule the search invalid because the search warrant hadn't specifically named the infant.

As the president perhaps too cleverly wisecracked, it was "because the baby hadn't given its permission to be searched." One assumes it was a wisecrack, since a valid search warrant doesn't require the permission of the searchee, old or young.

As the president left the story, the diapered baby affair is another silly example of the "technicalities" that often thwart the police. Never mind that the Fourth Amendment does, after all, insist that a valid search warrant must "particularly" describe "the place to be searched, and the persons or things to be seized." Never mind that the California judge considered it his duty to read the words literally.

Well, you might ask, where on earth did the constitutional protection of a diapered baby come from? Did James Madison find it, with the babies circa 1791, in a hollow stump? Or did the provision arise from the abuse by British colonial officials of "general" or non-specific warrants?

If you guessed the latter, you're on the right track. When the Bill of Rights was written, people had had their fill of random searches.

Should a child -- or an infant in diapers -- enjoy the privacy rights of an adult? If not, why not? A baby is a legal "person," even if a fetus isn't. Should the Fourth Amendment be constructively binding, as the Supreme Court has held, on local police as well as on federal law enforcement authorities?

Such questions may reasonably be asked, and answered in a variety of ways, without prejudice to the Fourth Amendment. It is more hazardous when responsible officials, even presidents, inflame uninformed prejudices against due process rights.

The requirement that search warrants "particularly" describe "the persons or things to be seized" is often a nuisance to the police. So are other Fourth Amendment restrictions.

But you can't understand why the Founding Fathers insisted on such requirements, despite their disadvantages, unless you remember the quarrel over general warrants in colonial times. That would be a valuable thing to understand, even if you are impatient about the results. When the understanding fades, the protection itself may not be far behind.