LAST MONTH a British jury refused to convict a civil servant charged with violating the Official Secrets Act. That law, a 1911 statute, had been invoked against Clive Ponting, a senior official of the Defense Ministry who sent two government documents concerning the sinking of the Argentine cruiser Belgrano to a member of Parliament. We do not have such a broad secrecy law in this country, and we don't want one. Two recent events, however, raise the possibility that British-type restrictions might be adopted here.

In an opinion released in Baltimore March 15, U.S. District Court Judge Joseph H. Young ruled that a 1917 espionage law could be used to prosecute a civil servant who sent classified photographs to a magazine. The statute has never been used successfully to prosecute in such a situation. No foreign agents or spies are involved in the case, and the government need not prove that the defendant acted with intent to injure the United States -- only that the material was properly classified and released without authority. Lawyers for the defendant, Samuel Loring Morison, a naval intelligence analyst, argue that the government should be able to discipline or dismiss him for this act, but not to prosecute him criminally under the espionage law. Judge Young's ruling simply allows the case to go forward, and if Mr. Morison is convicted, it will undoubtedly be appealed. But for the moment there is some doubt about the breadth of the 1917 law and how the Reagan administration intends to use it.

Within days of Judge Young's ruling, the White House confirmed a report in The New York Times that the CIA has proposed a secrecy law potentially as sweeping as the old British statute. The bill would make it a crime for a government employee to disclose to the press or other unauthorized people any classified information "that reasonably could be expected to damage national security." The proposal is believed to cover disclosures by members of Congress as well as by employees of the executive branch but would not make the publication of such material a crime. A draft of the bill is being circulated for comment by the Justice, State and Defense departments, and the administration has not yet decided whether to send it to the Hill.

The arguments against sweeping secrecy laws are familiar and persuasive. The difficulty always arises in determining which information is potentially damaging to national security and which is simply embarrassing to the government in power. Which whistle blowers do a service by forwarding information to Congress and the press and which -- can you think of a single case? -- actually put the country in jeopardy? In a society dependent on informed debate, the presumption must be that the work product of the government belongs to the people. The exceptions -- real military secrets, not, for instance, cost overruns -- must be few and far between and covered by carefully crafted statutes. Broad secrecy laws cripple a free society and must be resisted.