Eva Joly says that if François Hollande does not promise to shut down construction of the EPR reactor at Flamanville, there will be no electoral accord between her party and the PS. Of course, if Hollande does agree to Joly's ultimatum, Sarkozy will accuse him of succumbing to blackmail for a mess of pottage and of flip-flopping on the issue, since he has already committed to completing Flamanville if safety requirements are met.
This is typical behavior for the Greens, but as Cohn-Bendit has warned his party, politics by blackmail is a losing proposition. It enforces party purity but isolates the pure and renders them unsuitable as allies in a governing coalition, since governing is invariably an impure business. Non-negotiable demands may make partisans feel good but may disserve their ultimate goals. What is more, their ultimate goals may be wrongly conceived, and in this case I think they are.