(Adds details on ruling)
WILMINGTON, Del, June 27 (Reuters) - The Delaware Supreme Court ruled in favor of Chicago Bridge & Iron Co on Tuesday in its in $2 billion dispute with Westinghouse Electric Co that stems from cost overruns at a pair of unfinished U.S. nuclear power plants.
The two companies have been sparring over a 2015 deal in which Westinghouse, a unit of Japan's Toshiba Corp, bought the Shaw nuclear construction business of Chicago Bridge. Westinghouse later sought an adjustment to the closing deal price, sparking a dispute over accounting.
Westinghouse and Chicago Bridge agreed that an independent auditor would review post-closing adjustments to the deal price.
Tuesday's ruling directed a lower court to enjoin Westinghouse from raising claims before the auditor about Chicago Bridge's historical accounting before the deal was signed.
Chicago Bridge shares were up 14.5 percent at $16.50, on track for their biggest one-day percentage gain since October. The stock had tumbled 50.5 percent since May 8 as investors were anxious about the legal case as well was weak earnings.
Reporting by Tom Hals in Wilmington, Delaware; Editing by Bernard Orr