Further, the government suggests that the courts can't second-guess what constitutes a serious foreign-policy consequence, nor ask for specific evidence of wrongdoing.

They are arguing that "it's a blank cheque to the administration to declare anything contrary to our foreign policy, and then revoke people's visas and deport them", says David Cole,

who argued a similar case on behalf of Palestinian protesters that was litigated over two decades.

The law has rarely been used in this way. In a court brief, 150 legal scholars reported that the foreign-policy provision had been invoked in just 15 deportation cases since 1990, resulting in only four removals.

If its use of the 1952 law fails, the government has also argued that Mr Khalil is deportable for withholding information on his green-card application.

For precedent, the government's lawyers cite several cases from the 1950s when the perceived threats from communism often won out over First Amendment concerns.

Yet since then, in large part as a reaction to the trampling of rights during that Red Scare, the courts and Congress have strengthened free-speech protections for non-citizens.

The same law Mr Rubio is invoking to deport Mr Khalil was amended in 1990 to prevent deportation based on an immigrant's beliefs,

unless the secretary of state tells Congress that there is a compelling reason for deportation.

It is unclear whether Mr Rubio has done so, though he asserts that Mr Khalil's presence undermines America's policy of "combating antisemitism across the globe".

In a report explaining these changes at the time, lawmakers expressed hope that "this authority would be used sparingly

and not merely because there is a likelihood that an alien will make critical remarks about the United States or its policies".

The First Amendment makes no distinction between non-citizens and citizens. But the Supreme Court has tended to defer to the executive where immigration is concerned.

"For generations, there have been people on both the left and the right who have argued that the ordinary rules that apply in constitutional law generally don't apply when immigration policies are at stake", says Adam Cox of New York University.

For example, during Mr Trump's first term the court upheld the third iteration of the administration's travel ban on people from several muslim-majority countries, despite the ban's constitutionally questionable discrimination.

There are also doubts about whether the foreign-policy provision is too vague to be enforced.

How can an immigrant stay on the right side of the law when they don't know what might get them deported?

In a soap-opera-style twist, that was the conclusion of Mr Trump's late sister, Maryanne Trump Barry, then a district-court judge, when she ruled in 1996 that the measure was void because of its vagueness.

Her decision was overturned for procedural reasons.

But if Mr Khalil's case makes it to the Supreme Court, the justices could rely on her reasoning

and avoid confronting the question of whether executive power over immigration takes precedence over the free-speech rights of non-citizens.

While Mr Khalil's litigation plays out, Mr Rubio will no doubt continue revoking student visas.

Ms Aw says she expects to see students decide that studying in America isn't worth the stress.