By keeping its focus admirably tight, the sober and sobering Israeli documentary “The Law in These Parts” presents a devastating case against the occupation of the West Bank and the Gaza Strip. Investigating the legal system in the occupied territories, the film is fundamentally an inquiry into justice. It makes a forceful argument: Justice and the occupation are incompatible.

The director, Ra’anan Alexandrowicz, interviews only the lawyers, judges and generals who helped to create and then refine the laws, enforced by the military on a civilian population. Alexandrowicz, a questioning, sometimes goading off-screen presence, takes the men through case histories (a woman sentenced to prison for giving pita to a rebel fighter in hiding) and larger issues (when are rebel fighters terrorists, and when are they soldiers?).

We also hear how the law can be disturbingly malleable. If a law seems counter to international standards, those standards can be conveniently reinterpreted. (The most startling example has to do with establishing settlements on occupied land.)

As a filmmaker, Alexandrowicz is self-conscious, almost as a matter of principle. “This is the beginning of a documentary film,” he says at the start, and he continues to investigate the genre, pointing out its manipulations and elisions, just as he investigates the men he interviews. It’s as if he wanted to prove his honesty by insisting on his dishonesty, a strategy that occasionally backfires. When he stops to remind us that he has cut hours out of a particularly damning interview, don’t we start to wonder what complications have been left on the cutting-room floor?

His subjects may contort themselves, but Alexandrowicz doesn’t have to. His film makes a persuasive argument: When law is an alibi for power instead of a constraint on it, law has been emptied of all meaning.