Unless the son holds dual citizenship (which I don't think is the case) it would be impossible to strip him of his British citizenship, and as long as he remains a British citizen he has a legal right to abide in this country. Incidentally his father is Egyptian, not Yemeni.
"Unless the son holds dual citizenship (which I don't think is the case) it would be impossible to strip him of his British citizenship"
Not if the laws are changed.