Nobody should be jailed for reading extremist literature, the government's terror laws watchdog has said.
Clockwise from top left: Raja, Iqbal, Zafar, Butt and Malik
Lord Carlile said there must be "a real intention" to plan or commit an act of terrorism for a prosecution to proceed.
And it was "absolutely right" nobody was imprisoned "for mere thoughts, mere fantasies, mere wishes - even for their reading matter", the Lib Dem peer said.
On Wednesday the Appeal Court quashed convictions of five young Muslim men jailed over extremist literature.
The Lord Chief Justice said there was no proof of any intention to plan terrorist acts by the five - Irfan Raja, Awaab Iqbal, Aitzaz Zafar, Usman Malik and Akbar Butt.
They had been convicted last year by a jury at the Old Bailey, which heard the men became obsessed with jihadi websites and literature.
Lord Carlile, a Lib Dem peer who conducts independent reviews of laws on terrorism on behalf of the government, said it was "obviously right" that people were convicted if they were planning an atrocity.
But he stressed: "Otherwise, we do have to be careful about what one of the solicitors yesterday called 'thought crime'."
He told BBC Radio 4's Today programme that "what we should be concerned with is their actions and intentions, which can properly be criminalised".
"Nobody should be convicted of an offence unless they have a real intention; a purpose.
"And their purpose must be connected with the commission, the preparation or the instigation of an act of terrorism."