If Trump becomes President, it will be possible to revoke citizenship based on fraud (they lied while taking oath, are hostile to America), as well as rightly deny entry. We the People can hire AND fire, and Trump is the only one who seems to get that and state it in a variety of ways.
Perjury, also known as forswearing, is the intentional act of swearing a false oath or of falsifying an affirmation to tell the truth, whether spoken or in writing, concerning matters material to an official proceeding.
I've heard the traditional English punishment was to brand the palm of their right hand with 'P' for perjury... which is why one raises their right hand to take an oath.