Boris Johnson’s government is considering new measures to contain terror convicts after an Islamist freed from prison early stabbed civilians in Streatham, London.

Sudesh Amman, 20, was under active surveillance when he began stabbing people in Streatham, having been released on licence automatically halfway through an already short three-year sentence for terrorism offences.

The attack, which has now been claimed by the Islamic State, is the second to have been carried out by a terrorist freed from prison early in the last three months, with London Bridge killer Usman Khan having also been out “on licence” when he struck.

London Bridge Killer Usman Khan a Convicted Terrorist Released from Prison on Tag https://t.co/p5wfe2BhUK — Breitbart London (@BreitbartLondon) November 30, 2019

Automatic release at the halfway point in a custodial sentence is standard for criminals given determinate sentences in Britain, although alternatives are now available for more dangerous criminals, such as Extended Determinate Sentences — which make early release subject to a hearing, and applicable from the two-thirds point in a sentence rather than the halfway point.

Boris Johnson has said he intends to enact new measures to toughen sentences for “serious” terrorists and violent and/or sexual and prevent them from being released early — but this will not prevent the existing cohort of released terrorists and terrorists due for release from targetting the public.

There are reportedly at least 70 terrorists on the streets already, with Boris Johnson indicating that some 200 more are due for release, possibly in the near future.

“I think the question that everybody has about [Sudesh Amman] is what was he doing out on automatic early release, and why was there no system of scrutiny, no parole system, to check whether he was really a suitable candidate for automatic early release, and that is a very complex legal question,” Johnson told reporters at a press conference.

“[A]s you know we’re bringing forward legislation to stop the system of automatic early release — but the difficulty is… how to apply that retrospectively to the current cohort of people who qualify [for it],” he explained.

“We do think it’s time to take action to ensure that people, irrespective of the law that we’re bringing in, [to ensure that] people in the current stream do not qualify automatically for early release, [namely] terrorist convicts, people convicted of terrorist offences… you’ll be hearing shortly from the Justice Secretary, from Robert Buckland, about what proposals we intend to bring forward,” he added.

“The anomaly we need to clear up is the process by which some people are still coming out under automatic early release without any kind of scrutiny or parole system.”

Farage Demands Whole-Life Prison Terms for Terrorists Infected with 'Jihadi Virus' https://t.co/icv3FTbiDm — Breitbart London (@BreitbartLondon) December 2, 2019

Under the British constitution, in which Parliament is essentially all-powerful, there is no prohibition on retrospective legislation, although it is frowned upon — so there is nothing to prevent MPs from passing a law requiring existing terrorist prisoners to be kept in custody until they can satisfy the authorities that they do not pose a risk to the public.

There are anti-retrospective legislation provisions in the European Convention on Human Rights (ECHR), to which the United Kingdom is a signatory, meaning terrorists would likely attempt to appeal such against such a law in the European Court of Human Rights (ECtHR), but whether or not they would be successful is unclear, as retrospective criminal legislation such as the War Crimes Act of 1991 are already established on the British statute books.

1 in 3 cases lost by Britain at the European Court of Human Rights are brought by terrorists, prisoners or criminalshttp://t.co/AIUas080C6 — EFDD Group (@EFDgroup) August 18, 2015

Even this might not alleviate the threat posed by the dozens of terrorists who have already been released and cannot be monitored 24/7, however.

The Home Secretary, Priti Patel, might be able to use her powers to deprive some dual national terrorists and terrorists eligible for third-country nationality of their British citizenship in order to deport them — but the government has so far given no indication that it intends to pursue this course of action.

Follow Jack Montgomery on Twitter: @JackBMontgomery