The 19-year-old from London fled to Syria aged 15 and said she wanted to return to the UK with her newborn baby.
Here are some key questions about the case.
What has happened?
Mr Javid has used his powers under the British Nationality Act 1981 to strip Ms Begum of her British citizenship. This can be done in instances where doing so would be “conducive to the public good”. However, this power can only be used where the person concerned has dual nationality, as leaving an individual stateless is a breach of international law.
What is the law?
The power to revoke citizenship was extended by the Immigration Act in 2014 and can only be used in cases where a person has “conducted” themselves “in a manner which is seriously prejudicial to the vital interests of the UK” and where the secretary of state has “reasonable grounds for believing that the person is able, under the law of a country or territory outside the United Kingdom, to become a national of such country or territory”.
What was said about these powers when they were introduced?
Writing in the Daily Telegraph in 2014, then Home Secretary Theresa May said: “Following the recent Immigration Act, I can, in certain circumstances, remove citizenship from naturalised Britons who are fighting overseas and exclude them too. And while it is illegal for any country to make its citizens stateless, any British national who returns from Syria and Iraq faces prosecution here for participating in terrorist activities abroad.”
Does Ms Begum have dual citizenship?
Bangladesh’s minister of state for foreign affairs Shahriar Alam said she does not. He wrote on Twitter: “Bangladesh asserts that Ms Shamima Begum is not a Bangladeshi citizen. She is a British citizen by birth and has never applied for dual nationality with Bangladesh.
“It may also be mentioned that she never visited Bangladesh in the past despite her parental lineage.
“So, there is no question of her being allowed to enter into Bangladesh.”
What is the status of her child?
Guidance on British citizenship on gov.uk says “A child born outside the United Kingdom will be a British citizen by descent if either parent is a British citizen otherwise than by descent at the time of the birth.”
As Ms Begum was understood to be a British citizen as she gave birth, the child can also be considered a British citizen.
This appeared to be acknowledged by Mr Javid in the House of Commons when – not speaking about Ms Begum’s case specifically – he said: “Children should not suffer.
“So, if a parent does lose their British citizenship, it does not affect the rights of their child.”
Another sticking point may be the European Convention on Human Rights, with Article 8 guaranteeing the right to one’s “private and family life”. This could be used as an argument against any separation of mother and baby.