Conventional Christian theology holds that Heaven as a wall, and gates, if only metaphysical and metaphorical. Not everyone can get in. Presumably, the Pope holds to this, for otherwise why bother with all of the stuff Catholicism requires you to do? If anyone can get into Heaven, then eat, drink and be merry, and care not about anything at all. And, Hell is really easy to get into as well, having basically open borders. If one simply lived an anti-Christian life, then one is in. Now, how can the Pope be against borders between nations, or at least, once white Western nations? Surely to be consistent he will need to go the way of liberal Christianity and have open borders for Heaven. That means that immigration critics, and champions of walls will get into Heaven, to annoy him in the afterlife for all eternity! Cheer up, Popey.
https://www.breitbart.com/immigration/2019/04/07/pope-francis-praises-multiculturalism-migrants-always-bring-riches/
Migrants always bring riches? So, Trump was wrong about migrant crime? Ok.
https://www.bbc.com/news/world-europe-42557828