“It cannot be repealed”
let it be recorded in the laws of Persia and Media so that it cannot be repealed, that Vashti shall never again enter the presence of King Xerxes (Esther 1:19 BSB)
What it sounds like today
A routine legal formality about putting a ruling on the books.
The cultural key
The note that a Persian decree, once written into 'the laws of Persia and Media,' 'cannot be repealed' is not filler; it is the engine of the entire book. Persian royal law was regarded as irrevocable, binding even on the king who issued it (the same principle traps Darius into the lions' den decree in Daniel 6). So when Haman later manipulates the king into an irreversible edict to annihilate the Jews, the crisis cannot be solved by simply cancelling it. The only remedy is a second, equally permanent decree allowing the Jews to defend themselves. A modern reader wonders why the king does not just revoke the evil law; the answer is that, by Persian custom, he cannot.
Recovered meaning
Persian decrees, once recorded, could not be revoked, even by the king. That single legal fact is why Haman's death sentence on the Jews cannot be cancelled and must be answered by a counter-decree instead.