The independent reviewer of terrorism legislation said he will examine the use of anti-terror powers to detain David Miranda at Heathrow Airport, hours after police launched a criminal investigation based on the data seized.
David Anderson has written to Home Secretary Theresa May to outline his reasons for looking at Mr Miranda's detention at Heathrow on Sunday.
Mr Anderson said he wanted to establish if the power - contained in Section 7 of the Terrorism Act 2000 - was "lawfully, appropriately and humanely used".
ITV News correspondent Juliet Bremner reports:
The Home Office said in a statement that it was "right" for Mr Anderson to undertake such a review to ensure the law had been applied properly.
In separate developments, judges at the High Court were told a criminal investigation was now under way after police seized "tens of thousands of pages of material" from Mr Miranda's electronic equipment during his nine hour detention.
Scotland Yard said an initial examination "has identified highly sensitive material, the disclosure of which could put lives at risk."
"This [criminal] investigation is at an early stage and we are not prepared to discuss it in any further detail at this stage," a spokesperson added.
Mr Miranda was granted a limited injunction at the High Court today, preventing the Government and police from "inspecting, copying or sharing" data seized from him during his detention.
However, as the injunction still allows examination for national security purposes, his lawyer described the ruling as a "partial victory".
Guardian newspaper editor Alan Rusbridger said the decision to detain Mr Miranda "seems to me a clear misuse of a law."
Speaking at the Edinburgh International Book Festival, he said the "strong suspicion" has to be that his detention was "quite a carefully planned operation and wasn't random".