Previously, Hal, still wearing the Green Lantern ring, had stormed Wayne Manor alone. Alfred captured him, Aisha knocked off the Green Lantern ring, and Dick eventually picked it up.
The key lay in Aisha knocking off the Green Lantern ring. As explained before, a Green Lantern ring was like a safe, and what it stored was Green Lantern energy.
Only a Lantern recognized by the Green Lantern ring could open that safe and retrieve the Green Lantern energy within. This was part of the ring's security lock.
An ordinary person who had not been recognized by the ring could not open the safe or access its energy, even if they wore it. Nor could most people crack the Green Lantern ring's security lock.
What happened when Hal's ring was knocked off was, in detail, this: Hal used his status as a Green Lantern to pass the security verification and open the safe. Just as he was about to take something out, Aisha bit his hand, and the safe was thrown away.
But at that point, the safe was already open, and energy was continuously flowing out. Therefore, when Dick picked up the safe, he could immediately use the power of the Green Lantern. Even though he had not cracked the security lock or been recognized by the ring, he could still gain part of a Green Lantern's abilities.
After listening to Dick describe the entire process, Schiller guessed the principle behind it. The key was Aisha.
The Green Lantern Corps had operated throughout the universe for so many years that its security measures were fairly thorough. One rarely heard of an ordinary person getting lucky, picking up a ring, and then going on a killing spree.
Such accidents were rare precisely because the Green Lantern ring had a comprehensive security-lock