There may be rough poetic justice in the Supreme Court's decision to send R. Foster Winans off to prison for ''misappropriating'' the contents of a column he used to write for The Wall Street Journal.

Mr. Winans' journalistic ethics were, if you please, ratty. But even so, the court's judgment against him is bizarre and distinctly unfriendly to First Amendment values.

Winans is the 38-year-old former cowriter of The Journal's ''Heard on the Street'' column. The column's gossipy but well-informed ''reviews'' of stock issues often affected their prices, or were thought to do so. Four years ago, Winans conspired with two young Wall Street brokers to leak on some 27 occasions advance word of what the column would say. Using this purloined information, the two brokers made a killing in stock speculation -- some $690,000, of which they shared $31,000 with Winans.

The court's judgment, affirming that of a lower court, is that Winans' acts were not only unethical and disloyal (which no one would dispute) but also criminal: a form of wire and mail fraud.

To reach its strange conclusion, the court reasoned (in the face of a recent contrary ruling) that information can be ''property.'' It proceeded to treat the schedule and content of The Journal's ''Heard on the Street'' column as property ''owned'' by The Journal and capable of being misappropriated by a reporter.

This was not the result of a criminal complaint by The Journal. No newspaper, often dependent on information procured by dubious methods, could in good conscience complain that its own information had been ''stolen.'' Rather, the prosecution theory was the handiwork of that zealous scourge of ''insider trading,'' Rudolph Guiliani, the U.S. attorney for Manhattan.

The heart of Justice White's opinion is a transparently mistaken analogy. White borrows a model of ''ownership'' from corporate law, where certain kinds of trade secrets are protected by law against theft. He then applies it to the information gathered and disseminated by a newspaper (and by extension any organ of communication, print or electronic) in a way that is patently threatening to First Amendment values.

Newspapers and other journalistic organs have secrets, but not in the same sense that IBM, say, depends for profits on some bit of treasured technical information. Journalists are but temporary custodians of what is, or soon will be, in the public realm. Making its premature or unethical divulgence criminal is false to the essential purposes of journalism. Newspapers make money by spilling beans, not hoarding them.

The Supreme Court is usually careful to safeguard what Justice Holmes once called ''the free trade in ideas.'' But cases involving esoteric or unusual forms of information, carrying an aura of mystery, sometimes make the court forget itself.

That happened in the Snepp case some years some years ago. Snepp, a former CIA some years ago. Frank Snepp, a former contract employee of the CIA, published a book on the fall of Saigon. But he had not allowed the CIA to see it first, as his contract provided. The Supreme Court forced Snepp to disgorge his royalties. At least it did not send him to jail.

It is more than coincidence that White cites the Snepp case as a precedent for the Winans decision. What links the two is not that Snepp's information, or Winans', was essentially any different from any other; it is merely thought to be so by those who bow their heads reverently whenever someone uses talismanic phrases like ''secret intelligence'' or ''insider trading.''

Yet at Winans' trial it was agreed -- stipulated -- that the stuff he leaked to his confederates was not technically ''inside'' or privileged information of the sort whose misuse by securities dealers, lawyers or corporate officers is properly barred by the Securities and Exchange Act. It was only a journalistic concoction -- a me'lange of reporting, gossip, rumor and opinion, openly gathered, whose only effect on stock prices was that the investment community found it credible.

The Winans decision has disturbing implications for any reporter who ever uses a telephone indiscreetly. Imagine, for instance, that a reporter friend casually told you of his newspaper's approaching series on the B-1 bomber's defective navigation system. Imagine that you dashed out and sold your stock in the manufacturer. Is your friend liable to prosecution for fraud? Are you? If so, where is the injury?

That the Winans decision leaves such questions dangling is the mark of a casual indifference to key First Amendment values