WASHINGTON—A federal judge said the Food and Drug Administration doesn't have the authority to seize electronic cigarettes because the products don't qualify as devices subject to the agency's regulation.

In a 32-page opinion, U.S. District Judge Richard J. Leon sided with electronic-cigarette makers Smoking Everywhere Inc. and Njoy. He criticized what he called the FDA's "tenacious drive to maximize its regulatory power," saying he found its interpretation of the law "unreasonable and unacceptable."

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