When a gang member triumphs murder charges in his grandson’s death several times, a retired mob boss declares war against a young and powerful gang leader for control over the city’s corrupt legal system.

Dpg nailed it.

When his grandson's murderer is acquitted, a mobster comes out of retirement to get revenge on the murderer and the corrupt politicians who fixed the trial.
(26 words)

"When the murderer is of his grandson is acquitted, a retired Mob boss declares war on the man responsible a viscous young gang leader and his only choice is to put his old hit squad back together."