Welcome to immigration enforcement in first-world democracies. Too many loopholes, too many ways for people to skirt immigration laws and get into a country, nowhere near enough resources to find them, send them out, and keep them out. I am so glad I found a different job where I don't have to deal with that frustration.
Though I fully agree with pursuing the most dangerous ones as a priority, and it's a little silly for them to file a lawsuit claiming they're being ordered to break the law when it fact they're being ordered to focus their resources and continue to enforce the law with the resources at their disposal.