British citizens who go to live in foreign terror hot-spots like ISIS bride Shamima Begum could face up to 10 years in jail if they return to the UK.
The new laws come into force on Friday after the Counter-Terrorism and Border Security Act 2019 created a criminal offence of entering or remaining in a 'designated area' overseas.
The act was unveiled by the ministers last year as part of efforts to tackle the threat from so-called 'foreign fighters'.
It also allows Home Secretary Sajid Javid to designate an area, subject to parliamentary approval.
In order to use the power, he would need to be satisfied that it is necessary to restrict UK nationals and residents from travelling to or remaining in the area in order to protect the public from a risk of terrorism.
An individual found to have entered or remained in a designated area could face up to 10 years in prison if convicted.
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There are exemptions to people who have a legitimate reason for being in the area, such as journalists, aid workers or attending the funeral of a relative.
The offence does not allow retrospective prosecutions of individuals who have gone overseas to take part in fighting, such as those who went to territory held by Islamic State, before returning to the UK.
Mr Javid said: "These new laws give the police the powers they need to disrupt terrorist plots earlier and ensure that those who seek to do us harm face just punishment.
"As we saw in the deadly attacks in London and Manchester in 2017, the threat from terrorism continues to evolve and so must our response, which is why these vital new measures have been introduced."
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According to Home Office, more than 900 individuals 'of national security concern' from the UK have travelled to engage with the conflict in Syria.
And about 20 percent of them have been killed whilst overseas and around 40 per cent have returned to the UK.
The power to designate areas is one of a string of new anti-terror measures that come into force on Friday.
The legislation also:
-makes it illegal to "recklessly" express support for a proscribed organisation;
-creates an offence of obtaining or viewing terrorist material over the internet;
-extends extra-territorial jurisdiction for some terror-related crimes;
-increases maximum sentences for a number of offences.
