(Also since you brought up Obama, why was Obama able to deport so many more people than Trump? And able to do it without terrorizing US cities with secret/poorly trained police, or needing a DHS with a larger budget than most other countries' militaries?)
You're fixated on a "technically this is legal" argument. But you're (perhaps willfully) missing the larger repercussions. This administration has lied and misled about their opponents committing fraud. You know they are not acting in good faith. So why would we want to further empower capricious, inconsistent, and politically motivated behavior?