Very few members of the public actually get this point. The "immigration amnesty" is being put through with sheer hustle. It's a scam. Smoke and mirrors.
The immigration officials have been ordered "not to prosecute," that is, "not to deport."
I believe that if it was just an order not to enforce, the executive action would be valid. But it goes much beyond that. It basically extends the rights and benefits of a citizen on the specified illegals. That is proactive and that's what is being challenged.