Michael Price on Lawfare discusses a specific problem the Muslim ban will encounter in the courts, at least so long as Trump tries to use § 212(f) of the Immigration and Nationality Act (INA):
And in 1987, Congress responded by passing the “Moynihan-Frank Amendment,” explicitly prohibiting the President from excluding foreigners based on their beliefs. The provision became permanent with the enactment of the Immigration Act of 1990, as codified in § 212(a)(3)(C)(iii). The statute made clear Congress’s intent to end the practice of ideological exclusion. As the Senate Foreign Relations Committee put it:
For many years, the United States has embarrassed itself by excluding prominent foreigners from visiting the United States solely because of their political beliefs. Among those excluded, or harrassed [sic], in recent years have been Nobel Laureates Gabriel Garcia Marquez and Pablo Neruda, and authors Graham Greene, Doris Lessing, and Carlos Fuentes. In these cases and others, the excluded individuals had done no more than exercise rights to freedom of expression and association enshrined in the Universal Declaration of Human Rights – rights promoted in congressionally-initiated human rights legislation and constitutionally protected for all U.S. citizens.
S. Rep. No. 100-75 at 11, 100th Cong., 1st Sess. (1987). The House similarly decried the Executive’s use of immigration law to deny American citizens “the opportunity to have access to the full spectrum of international opinion,” stating that “the reputation of the United States as an open society, tolerant of divergent ideas, has suffered.” H.R. Conf. Rep. No. 100-475 at 162-63, 100th Cong., 1st Sess. (1987). Indeed, according to the legislative history, the whole point was “to take away the executive branch’s authority to deny visas to foreigners solely because of the foreigner’s political beliefs or because of his anticipated speech in the United States”—in what the Senate Report deemed an “affirmation of the principles of the First Amendment.” S. Rep. No. 100-75 at 11.
His conclusion?
Section 212(f) is not a blank check, and at least to date, it has never been used for the purpose of ideological exclusion. Moving forward, the big question for the courts will be whether President Trump’s executive order runs afoul of the will of Congress and infringes on the constitutional rights of Americans. There is a good case to be made that it does.
Congress long ago placed limits on Presidential power in the wake of well-documented abuses, and fortunately the Federal courts, more or less immune to the winds of political whimsy, are usually willing to enforce the laws as necessary.