Threatening (again) to withhold funding to “sanctuary cities” is ridiculous. You don’t withhold funding to criminals, you arrest them.
You might want to find what can be done within the law and keep in mind that the courts are already involved.
Have you been paying attention to the six month saga of the president's travel ban? There always seems to be a lefty judge who will complicate the administrations plans as long as possible. The DOJ is going after the sanctuary cities however they can within the law.