A French court on Wednesday turned down a U.S. request for the extradition of an Iranian engineer who is accused of violating an export embargo by purchasing U.S. technology for military firms involved in Iran's nuclear program.

The United States says Majid Kakavand, 37, bought sensitive American electronics over the Internet and disguised that their final destination was Iran by routing them through Malaysia, where he had set up a front company.

Kakavand's case and several others have showcased how the United States is doggedly going after people accused of procuring technology or weapons for Iran's military, in many cases seeking help from foreign countries.

Yet the court's ruling shows that such cooperation is not simple. Kakavand's case has dragged on for 14 months since his arrest as officials tried to determine if his business dealings violated French law as well as U.S. law. The court could not hand him over merely for breaking U.S. laws that have no counterpart in France.

The case has sensitive diplomatic implications in three countries — especially in France, which has taken a tough stance on Iran's nuclear ambitions but nonetheless has business and oil interests there. Another source of diplomatic tension is the case of a young French academic in Iran who pleaded innocent to spying charges at a mass trial.