A federal judge said Thursday the Food and Drug Administration cannot stop shipments of electronic cigarettes into the United States.

The preliminary ruling by U.S. District Judge Richard Leon came as California Attorney General Jerry Brown sought in a state court to halt one company's sale of electronic cigarettes. Brown says the e-cigarettes contain dangerous chemicals and are being marketed to children.

E-cigarettes operate with a heating element and a battery. Users inhale a vaporized liquid nicotine mixture much the way traditional smokers inhale smoke.