Across Latin America in recent years, citizens have tossed out one government after another in search of honesty and accountability. Yet reformers have mostly failed to break entrenched cultures of graft and impunity. A novel approach in Guatemala might break that trend.

The Central American country’s recently installed new president, Bernardo Arévalo, on Monday submitted a bill he hopes will strengthen judicial independence by making the attorney general’s office more accountable to the public and less vulnerable to political influence. It coincides with a raft of additional measures opening government procurement to scrutiny and shielding anonymous whistleblowers from prosecution.

On the surface, such reforms make as much sense as jousting with windmills. The president’s party has too few legislators to enact his agenda on its own. The current top prosecutor, meanwhile, is a fierce opponent of corruption reform, with powerful allies on the courts and in Congress. Delay is costly. The constitution bars reelection, which gives Mr. Arévalo just four years to change Guatemala’s governing norms.