A former requirement no longer applies; release the listener from it.
序 · The move
1Place 無須 before the verb, not before a noun.Is what follows an action, not an object? 無須 negates doing, not having.
2State the action that is now unnecessary.Could it be reframed as 不必 or 不用 with the same sense? If yes, 無須 fits; it is the written register of that meaning.
3Leave the rest of the clause positive.Is the obligation the only thing negated, and the verb itself left to stand?
例 · Examples
1政府government蓋to build了一條新的道路road後after，居民residents無須need not再any longer繞遠路take the long way around。
After the government built a new road, residents need not take the long way around anymore.
Both say no need to. 不用 is everyday speech; 無須 is the written, formal register for the same release.
不要
不要 forbids the action (don't do it); 無須 lifts the requirement (you may, but there is no need).
✗ 居民無須遠路 → ✓ 居民無須繞遠路 (無須 takes a verb, not a bare noun)
✗ 你無須去嗎 → ✓ 你需要去嗎 (無須 states a release, it does not ask a question)
✗ 無須他來 → ✓ 他無須來 (the subject under release comes before 無須)
English no need to lets the subject stay implicit (No need to worry); 無須 still sits after its subject and before a verb, never alone as a standalone reply.