Step 1: Read the question.
Section 5 of the Arbitration and Conciliation Act, 1996 limits how far a court can step into arbitration. We must find the one situation in which a court may step in.
Step 2: Understand the main idea of the Act.
The Act rests on party autonomy and minimal court interference. The parties chose arbitration to settle their dispute quickly and on their own terms, so courts should not interfere unless the law clearly allows it.
Step 3: Read Section 5 carefully.
Section 5 says that in matters governed by Part I, no judicial authority shall intervene except where such intervention is expressly provided in this Part. So the test is simple, the court can act only where the Act itself permits it.
Step 4: See where the Act allows intervention.
The Act expressly allows courts to act in fixed situations, for example appointing arbitrators under Section 11, granting interim measures under Section 9, and setting aside an award under Section 34. These are written into the Act.
Step 5: Check the wrong options.
Option (A) is wrong because a mere request by both parties cannot enlarge the court's power. Option (B) is wrong because an alleged procedural irregularity without a specific provision does not allow intervention. Option (C) is wrong because a court cannot re-examine facts just because it feels the award is unjust.
Step 6: Conclude.
A court may step in only when the Act expressly permits such intervention. That is the correct answer.
\[ \boxed{\text{When the Act expressly permits such intervention.}} \]