Good piece by David Graham of The Atlantic on one of the Republican obsessions.
And an obsession, of course, that the Conservative government pursued with respect to citizenship revocation for terror or treason (in the process of repeal by the current government) and birthright citizenship, where they tried to end the practice but gave up provincial opposition due to the high cost compared to the small numbers involved:

Depriving someone of their citizenship is one of the harshest sanctions a government can levy—not as lastingly grave as execution or life imprisonment, perhaps, but still very serious, especially for someone who is not a dual citizen and would therefore be left stateless. (It’s a situation that Edward Everett Hale dramatized in his famous short story “The Man Without a Country,” published in The Atlantic in December 1863.)

Yet recent years have seen a vogue among Republicans for proposing to strip citizenship as a punishment for various crimes. In 2014, Senator Ted Cruz, a Trump frenemy-turned-enemy-turned-supporter-turned-rumored-appointee, proposed stripping citizenship from any American, native-born or naturalized, who declared allegiance to a foreign terrorist organization, became a member of such an organization, or provided training or material assistance. Senator Rand Paul floated a similar proposal around the same time. Earlier this year, Newt Gingrich, a close Trump adviser, called for stripping citizenship from and deporting any Muslim who believes in sharia law, a proposal that is impractical, nonsensical, and virtually guaranteed to be unconstitutional. Somewhat more perplexingly, Ben Carson called in a 2014 column for non-citizens who vote fraudulently to be stripped of the citizenship they don’t possess.

 A different but related current is the occasional call, usually from Republicans, for an end to birthright citizenship, which grants American citizenship to anyone born in the United States—most notably to the children of immigrants, whether authorized or not. Ending birthright citizenship was one of the earliest policies that Trump rolled out in the summer of 2015, saying, “This remains the biggest magnet for illegal immigration.” Several of his rivals for the Republican nomination announced that they agreed with him.The frequent proposals from conservatives and Republicans to strip citizenship as a punishment for a range of crimes—or in the case of birthright citizenship, for the crimes of one’s parents—illustrates a partisan difference in how citizenship is viewed. Progressives tend to think about citizenship as a right that, if acquired legally, cannot be taken away, even for heinous crimes. It is nearly absolute. Conservatives, however, tend to view it as a privilege, and while it might be the default, it can still be withdrawn, as in the case of Americans who join terrorist groups. The right tends to view the left’s version as insufficiently patriotic, but it’s simply a different view of patriotism, and perhaps one that is more constitutionally grounded.

(In a separate and controversial move, President Obama decided he could kill American citizens fighting for terrorist groups overseas, such as the radical cleric Anwar al-Awlaki, without trial—thus depriving Awlaki of another of his rights—a decision that was decried by civil libertarians.)

Birthright citizenship is one of those areas in which the United States is unusual—even exceptional. Just 33 countries around the world offer it. The legal matter has been more or less settled since 1898, when the Supreme Court ruled that children of foreigners who are born in the United States are, according to the 14th Amendment, citizens, though some scholars have argued that does not cover unauthorized immigrants.Stripping citizenship is another area in which the United States has taken an exceptional stance. Governments from oppressive Middle Eastern police states to Western European countries have used the tactic as a punishment for various crimes. Libertarian journalist Matt Welch suggested in late 2015 that there’s a global trend toward it. In 2014, the United Kingdom established the maneuver for terror suspects, and Australia did the same a year later. French President Francois Hollande this year dropped a similar proposal, brought up after terror attacks in 2015, in the face of opposition.

Doing the same in the United States would likely be impossible. The Supreme Court ruled in Afroyim v. Rusk in 1967 that American citizens could not be stripped of their citizenship involuntarily. Wikipedia has a useful though incomplete list of those who have had their citizenship stripped. Generally, those cases in recent decades fall into a three clear, sometimes overlapping, groups: spies, former Nazis, and those who acquired their citizenship fraudulently, i.e., by lying during the naturalization process. Even Emma Goldman, the famed anarchist leader, was stripped of her citizenship not explicitly for being an anarchist, but on a technicality: She had obtained citizenship through marriage to a man who was a naturalized citizen, and the government determined that the ex-husband had fraudulently obtained his citizenship, thus invalidating hers as well.

Throughout the 1950s, as Atossa Araxia Abrahamian wrote in Dissent in 2013, there were plenty of cases of Americans, both naturalized and native-born, who were stripped of their citizenship for having various foreign ties. But the Supreme Court eventually stamped that practice out in Afroyim. Some conservative legal scholars have argued for a new legal regime in which citizenship could be stripped in certain circumstances. Richard Epstein, a law professor at the University of Chicago, frames the conservative case for citizenship as a privilege this way:

“Think of the United States as a quasi-partnership, which has to set its rules for the admission and exclusion of its member citizens. I know of no private association that states that an individual can lose his place in the firm only if he voluntarily resigns. Virtually every well-drafted agreement understands that these relationships depend upon trust, and thus allows a forcible removal for cause.”

Epstein reasons, “The same for-cause rule applies to common carriers who have to take all customers on reasonable and nondiscriminatory terms. Even they can exclude rowdy or drunken individuals.” Whether something as fundamental as citizenship should be treated similarly to the right of an unruly, besotted patron to get one more nightcap is a matter on which people are likely to disagree.

In any case, adopting Epstein’s point of view would require a Supreme Court decision overruling the Afroyim precedent and returning the United States to the system more as it was in the 1950s and 1960s. Trump is likely to have a chance to make some at least one Supreme Court appointment; perhaps this is the America to which his campaign slogan suggested returning.