“(3) Subject to paragraphs (4) and (5), a person who has been admitted to, or acquired a right to reside in, the United Kingdom under these Regulations may be removed from the United Kingdom if- …. he would otherwise be entitled to reside in the United Kingdom under these Regulations but the Secretary of State has decided that his removal is justified on the grounds of public policy, public security or public health in accordance with regulation 21. ”
“taking into account past conduct of the person and that the threat does not need to be imminent;”
“(f) the decision may be taken on preventative grounds, even in the absence of a previous criminal conviction, provided the grounds are specific to the person.”
“(8) A court or tribunal considering whether the requirements of this regulation are met must (in particular) have regard to the considerations contained in Schedule 1 (considerations of public policy, public security and the fundamental interests of society etc.).”
“(5) Where a deportation order is made against a person but the person is not removed under the order during the two year period beginning on the date on which the order is made, the Secretary of State may only take action to remove the person under the order at the end of that period if, having assessed whether there has been any material change in circumstances since the deportation order was made, the Secretary of State considers that the removal continues to be justified on the grounds of public policy, public security or public health.”
‘imperative grounds of public security’