IANAL, but while lawful permanent residents do not have the same protections, they still have certain protections that make it legally unclear whether the president can categorically bar entry without an immigration court proceeding for each individual:

"Section 212(f) can certainly apply to applicants for immigrant visas. Whether it can apply to an LPR who is returning and not seeking admission is questionable. This is because under section 101(a)(13)(C), an LPR being covered by a Presidential Proclamation under section 212(f) would not cause the LPR to be considered to be seeking admission."

http://myattorneyusa.com/scope-and-history-of-section-212f-p...

"An alien returning to the United States who has been granted lawful permanent resident status cannot be regarded as seeking an admission and may not be charged with inadmissibility under section 212(a) of the Immigration and Nationality Act, 8 U.S.C. § 1182(a) (2012), if he or she does not fall within any of the exceptions in section 101(a)(13)(C) of the Act, 8 U.S.C. § 1101(a)(13)(C) (2012)."

https://www.justice.gov/eoir/file/478111/download