Simmons was dealt a setback in his bid for NL.

A federal appeals court temporarily blocked Dallas investor Harold Simmons from pursuing his hostile bid to acquire NL Industries, giving the company a chance to restore its “poison pill” takeover defense. The poison pill is a provision adopted by NL’s directors to thwart an unwelcome takeover, and the measure was struck down Tuesday by U.S. District Judge Vincent L. Broderick. Simmons triggered the plan by acquiring more than 20% of the chemical and oil field services firm’s stock, and had asked the court to invalidate the plan. Simmons has offered $15.12 1/2 a share for the remaining stock, or a total of $723 million.