[mike_hearn]

> An agency interpreting the law that governs their mandate is at least nominally trying to do so in a manner that yields effective policy

Ideally. In practice ambiguities in statutes governing agency mandates are always interpreted by agencies in whatever way would maximize their own options and power. That's the written justification for the APA in the first place: reeling in excessive "zeal" amongst administrators.

The courts don't get powers from the law directly (except meta-powers like the one this case is about), so there's no direct benefit to judges from interpreting law in a maximally agency-advantageous way. That's why countries (not just the US) have courts resolve ambiguous law. It's a core part of their job.