A Brazilian federal court on Thursday granted an injunction blocking the proposed tie-up between U.S. plane maker Boeing Co and Embraer SA, a deal the Brazilian company says is crucial to its survival.

The decision forbids Embraer’s board of directors from signing the deal to create a joint venture on commercial aviation that Boeing would control.

The legal action was brought by four congressmen with Brazil’s left-wing Workers Party.

In July, the companies inked an agreement in which Boeing would acquire 80% of Embraer’s commercial aviation business.

Boeing and Embraer have also interest in broadening their partnership on the Brazilian firm’s KC-390 cargo plane.