The transaction has already been approved by Chevron's shareholders and cleared by U.S. regulators, but its fate now rests on the tribunal's interpretation of a joint operating agreement drafted more than a decade ago. In anticipation of a positive outcome, Chevron has bought roughly 5% of Hess's outstanding shares in the open market. Traders and hedge funds are also heavily invested, with more than $10 billion worth of Hess stock purchased by merger-arbitrage funds betting on a favorable ruling.