It’s the up to Congress to pass legislation invalidating the executive order, which is then subject to Presidential veto, or the courts to declare the order UnConstitutional.
It's actually funny. Sanders, as a socialist, was actually for closed borders and sending illegal immigrants back. Because he understands that while there are huge numbers of unskilled people, then big businesses have no incentive to raise wages or support better rights. But now that there is less immigration, wages can rise and employers don't have the upper hand. Of course now Sanders has come around to the insane proposals of The Left about ICE and immigration.
I don't think Paul understands that you and I view Sanders as just promising free things without offering information on how to fix things. Education is the perfect example. What's the point of cancelling student debt if one is not going to look at how American universities have raised prices so much. Is it in the tax payer's interest to support the bloat? No.