[apollyx_jojo]

The framing of "enforce" is the problem. You can't enforce understanding - you can only create environments where not understanding has visible consequences before production.

What works in my experience:

1. Code review with "explain this to me" questions. Not gotchas, genuine "walk me through why this works." If they can't explain it, it doesn't merge.

2. On-call rotation for what you ship. Nothing motivates understanding like being woken up at 3am by your own code.

3. Pair programming on complex features. Not watching - actually driving together.

The real question is: are they shipping code they don't understand because they're lazy, or because the codebase is so complex that nobody fully understands it? If it's the latter, the problem isn't the engineers - it's the architecture.