The way their grandparents and great grandparents back did - Immigration done "the right way" was coming over decades ago when legal immigration was based on quotas and the color of your skin.
I'm "this close" to asking the office MAGA of Mexican heritage (but light enough to pass as European) why his grandparents "worked the right way" to become Naturalized US citizens (which happened in the 1980's), and what the difference was between their immigration then and immigration now.
Did they have to go back to Mexico for 10 years and apply from there and wait until they were initially adjudicated and given a visa and permission to come across?
Or did Gramps come across the border and get a visa to work, and was able to stay in the country with his Mexican wife and later kids born here while he and his wife went to years classes and immigration hearings to get their Green Card?
How many times were they -and their cohort of "proper way legal immigrants" - able to stay in the country and keep their visas, even if the paperwork got messed up, or they might have missed hearings or had lapses due to schedule and work conflicts, becoming technically "undocumented"? How many of them had temporary deportation orders issued until they could get a hearing and have it rescinded.
My naturalized neighbor and his wife became citizens in the 90's. It was tough, yes, but they knew they weren't going to be deported just because of a paperwork SNAFU or a missed appointment.
The Amnesty program worked the same way back then. Come over, ask for Amnesty, get a sponsor, get your record # to show law enforcement from the immigration court clerk, and make it to your appointments.
Oh, yeah. MAGA decided to change the process that about 7 million people are legally here now because too many "undeserving" people had been abusing the process for almost a century...
His Grandparents are dead now, they don't have to worry about being sent back to Mexico for a missed traffic ticket or mis-identification.
On edit - my Maternal Great Grandfather and his brothers "jumped ship" in Massachusetts coming over from Vasa (Finland) escaping a Tsarist Russian draft in the 1890's by signing on as crew on a Swedish ship bound for New York.
They didn't want to go through Ellis Island and risk being sent back.
They ended up making friends with someone who got them a job in Pennsylvania, and were identified as US citizens born in Finland on the 1910's census.
I don't think that would have been considered legal today...