ABSTRACT
The power to admit, exclude and expel aliens was among the earliest and most widely recognized powers of the sovereign state, and the power remains 'undoubted'. But unless it is understood to be a constitutional principle, or the instrument of constitutional principle, the power will crumble, eroded by newly enforceable constitutional principles of equality before the law, and by rights as ancient as liberty or as newly fecund as respect for private life. The legislation made by or under parliamentary authority during the first twenty years of the twentieth century defines principal effects of the constitutional distinction between nationals and aliens. Risks to the public good that must be accepted when posed by the potential conduct of a national need not be accepted when posed by a foreigner, and may be obviated by the foreigner s exclusion or expulsion.
