As I’ve noted previously in this space, the Justice Department has been strenuously ramping up prosecutions under the Foreign Corrupt Practices Act, the law that criminalizes many of the sorts of official payments that alas typify the business climate across much of the globe. Per Shannon Green at Corporate Counsel, “2011 Was a Banner Year for FCPA Enforcements and Trials.” Unfortunately, as I argued in that earlier post, the law is so vague, uncertain and unpredictable in its reach that many businesspersons risk prosecution even though it is far from clear that their actions actually did violate the law.

Don’t just take my word for it: ask federal judges. Over the past two months alone they’ve thrown out three high-profile FCPA prosecutions in whole or part after finding the Department hadn’t proved its case.

On Monday U.S. District Judge Lynn Hughes in Houston, after hearing the prosecution case, dismissed the jury and summarily tossed out DoJ’s 12-count FCPA indictment against John O’Shea, an executive with the Swiss engineering company ABB Ltd., over allegedly improper payments in Mexico. Judge Hughes “said O’Shea’s conduct was reasonably explained by lawful motives,” to quote FCPA Blog. He also dismissed a conspiracy count. C. M. Matthews at the WSJ’s Corruption Currents Blog has more on the case. (O’Shea continues to face some other counts, in particular under the federal “money laundering” statute, itself a case study in rampant overcriminalization.)

Last month district judge Richard Leon in Washington, D.C. dismissed conspiracy charges against six defendants caught in an African arms-trade “sting” operation, which resulted in the outright acquittal of one of the defendants, Stephen G. Giordanella, who unlike the others faced no substantive FCPA charges. Earlier, Judge Leon criticized federal prosecutors for “sharp” tactics in handling evidence of interest to the defense.

And DoJ’s most stinging embarrassment of all came last month as well, when federal judge Howard Matz in Los Angeles – quoting the WSJ again – “threw out the landmark FCPA conviction of Lindsey Manufacturing Co., the first company convicted under the law, and offered a scathing assessment of the Justice Department’s handling of the case.” Specifically,

it is with deep regret that this Court is compelled to find that the Government team allowed a key FBI agent to testify untruthfully before the grand jury, inserted material falsehoods into affidavits submitted to magistrate judges in support of applications for search warrants and seizure warrants, improperly reviewed e-mail communications between one Defendant and her lawyer, recklessly failed to comply with its discovery obligations, posed questions to certain witnesses in violation of the Court’s rulings, engaged in questionable behavior during closing argument and even made misrepresentations to the Court.

Efforts to reform the substance of FCPA are picking up steam in Congress, and that’s all to the good. But equally or more vital to the public liberty is countering the danger of out-of-control federal prosecution, which we’ve seen lately in fields ranging from environmental enforcement to dubious obstruction-of-justice charges. Isn’t it time for Congress to use its oversight powers more vigorously?