MARVIN MANDEL, the former governor of Maryland who was convicted on mail fraud and racketeering charges 10 years ago, declares that he has been vindicated. On Thursday, a federal judge in Baltimore threw out his conviction, and those of his codefendants, which arose from a kickback scheme alleged to have netted the governor hundreds of thousands of dollars in exchange for support of legislation to extend the racing season at the Marlboro Race Track. The judge did not find that this arrangement had never existed. He specifically says that the "evidence of concealment of ownership of Marlboro shares and of Mandel's secret financial arrangements certainly showed that something fishy, and perhaps dishonest, involving Maryland's governor and some of those personally and politically closest to him was going on." Nevertheless, the judge found that no federal crime was committed because the mail fraud statute under which the indictments were brought covers only fraud involving loss of money or property, not intangible rights such as good government.

This decade-late review of the Mandel case would never have come to court except for a bombshell dropped by the Supreme Court last June. For many decades, federal prosecutors had used the mail fraud statute to go after corruption of many kinds. Use of the mails to deprive citizens of good government, by taking kickbacks, for example, or fraudulently obtaining and casting absentee ballots or conspiring to bribe public officials -- even though none of these involved depriving citizens of money or property -- was considered to be a violation of the statute. Every federal court that heard these cases -- the statute has been on the books for 115 years -- had approved this interpretation of the law. This summer, though, the Supreme Court, on a 7-to-2 vote, ruled that the law could only be used in cases involving loss of money or property. Prosecutors howled and predicted that they would be hamstrung in prosecuting corruption cases, and for the time being at least, they are probably right. They also foresaw that many old convictions under the statute -- like Mr. Mandel's -- would be overturned.

One should be wary of broad, somewhat vaguely defined criminal statutes designed to rope people in when the underlying substantive offenses cannot be proved. The conspiracy statutes can be misused in this way, as can the racketeering laws. And although Marvin Mandel and his friends may have done "something fishy and perhaps dishonest," fishy and perhaps dishonest don't make a criminal case. The Supreme Court was right in observing that when a criminal statute is capable of being interpreted in different ways, courts have an obligation to view it in the light most favorable to a defendant.

So the ruling was a good one, and Mr. Mandel has received an unexpected benefit. But this does not mean that all kinds of corruption by state and local officials shouldn't be prohibited by federal law. Congress should act to rewrite the mail fraud statute in unambiguous terms so that conduct everyone agrees is wrong will also be clearly illegal under federal law.