Well, technically everyone who enters from Mexico illegally is a criminal, and he certainly wanted to put a stop to that. He was also not to keen on immigrants from Muslim countries. For instance:
"When I’m elected I will suspend immigration from areas of the world where there’s a proven history of terrorism against the United States, Europe or our allies until we fully understand how to end these threats. After a full …
(APPLAUSE)
Thank you.
And by the way we have no choice. After a full and partial and long — really long overdue security assessment we will develop a responsible immigration policy that serves the interests and values of America."
After his election, there was Executive order 13769, replaced by EO 13780 (for reasons of constitutionality, as I recall):
"Executive Order 13769 lowered the number of refugees to be admitted into the United States in 2017 to 50,000, suspended the
U.S. Refugee Admissions Program (USRAP) for 120 days, suspended the entry of
Syrian refugees indefinitely, directed some
cabinet secretaries to suspend entry of those whose countries do not meet adjudication standards under
U.S. immigration law for 90 days, and included exceptions on a case-by-case basis. The
Department of Homeland Security (DHS) listed these countries as
Iran,
Libya,
Somalia,
Sudan,
Syria,
Yemen.
Iraq was also included until it was dropped following sharp criticism from the Iraqi government and promises of improved vetting of Iraqi citizens in collaboration with the Iraqi government.
[6][7] More than 700 travelers were detained, and up to 60,000
visas were "provisionally revoked".
[8]
(of course, from Wikipedia)
I recall all of this kerfuffle very clearly because my friend was dating a Syrian refugee who was about to get sent back, so they got married lickety-split. Other of my muslim friends who were from the countries mentioned (or other countries with muslim populations) were afraid to leave the country, even for business, thinking they might not get back in. Also, I knew some young people who were in the 'Dreamers' status, who thought they might get deported to countries they didn't even remember. (
discussion, that was also overturned by the court).
Maybe I just remember it because I have a bunch of immigrant friends who were in a panic.