This week could mark the most consequential development on the U.S.-Mexico border since January 2021, when President Joe Biden essentially opened the nation's doors to millions of illegal border crossers. On Wednesday, Title 42, the Trump-era measure that allows the U.S. government to quickly return illegal crossers to Mexico on the grounds of preventing the spread of COVID, will expire. After that, officials expect a flood of illegal crossers, all coming into the United States confident that they, like hundreds of thousands before them just this year, will be allowed to stay.