“Lā tuṭiʿ amrī” can be a threat, but not every stern utterance abandons its literal meaning.
Genuine prohibition: A supervisor says “Lā tadkhul” — Do not enter. Entry is actually forbidden.
Permission: Someone says “In shiʾta fa-lā taʾti” — If you wish, you need not come. It may offer a choice.
Threat: An angry superior says “Lā tuṭiʿ amrī” — Disobey my instruction and face the consequences.
The distinction depends on evidence of forbidding, allowing, or warning of harm, not the presence of lā alone.