It was a dreary January afternoon, and George Kahale was looking forward to a relaxing deep-tissue massage and some decompression in the steam room at his Manhattan gym. After months of travel to Kazakhstan and round-the-clock negotiations over development of its Kashagan oil field, this Saturday afternoon off was a rare treat for the managing partner of Curtis, Mallet-Prevost, Colt & Mosle.

Alas, it was not to be. As Kahale stepped out of his East Side apartment building, he heard the familiar ring of his BlackBerry. A senior official of Venezuela’s state oil company, Petróleos de Venezuela, S.A. (PDVSA), an important Curtis Mallet client, was on the line. The company had just received a fax from Exxon Mobil Corp. The Texas-based oil giant had won an order from a London court freezing $12 billion of PDVSA’s assets.

"It wasn’t clear what had happened exactly," Kahale recalls. For more than a year PDVSA had been in tense negotiations with Exxon. Venezuela wanted the American company to renegotiate its contract to develop a Venezuelan oil field. Kahale says he wouldn’t have been surprised if Exxon had filed a notice of intent to arbitrate the dispute. But "this was different," he says. Indeed, a British court freezing billions of assets without notice was highly unusual.