continuity, you’ve read that incorrectly. What it says is
5. Subject to the provisions of section 3 a person born after the commencement of this Act, shall be a citizen of Bangladesh by descent if his 4[ father or mother] is a citizen of Bangladesh at the time of his birth:
Shamima’s parents are both citizens of Bangladesh by birth. So Shamima is automatically a citizen of Bangladesh by descent. Citizenship by descent is given to the children of first generation migrants who were not born in Bangladesh but whose parents were. I’m that case it is automatic.
Provided that if the 5[ father or mother] of such person is a citizen of Bangladesh by descent only, that person shall not be a citizen of Bangladesh by virtue of this section unless-
(a) that person's birth having occurred in a country outside Bangladesh the birth is registered at a Bangladesh Consulate or Mission in that country, or where there is no Bangladesh Consulate or Mission in that country at the prescribed Consulate or Mission or at a Bangladesh Consulate or Mission in the country nearest to that country;
These two sections (which I think you misunderstood) refer to the children of second generation migrants. So children whose grandparents were born in Bangladesh, but whose parents were not. So their grandparents are ‘citizens by birth’ of Bangladesh (as Shamima’s parents are) but their parents are citizens of a country other than Bangladesh (citizens by descent of Bangladesh). In the case of children of those with citizenship by descent, citizenships is not automatic and the birth would need to be registered with the Bangladeshi governments representatives in the country of their birth in order for them to receive it. This will apply to Shamima’s son.
Shamima’s however was automatic, no registration required.
It doesn’t matter how many knots people try and pull themselves into to make her a British citizen, or how many half understood links they want to post. She is a Bangladeshi citizen now, not a British one. And it’s all perfectly legal.
Basically Shamima thought she was being clever and her lawyer thought he smelt big bucks and that we would be forced to take her back regardless of how obvious she made her support for ISIS because neither of them had done their research. She’s fucked. No wonder she’s started furiously back pedalling and saying she’s willing to change now.