@oralloy,
The Congress can fund anything they want. And Trump can veto it.
The problem is that Trump is using his veto power to force Congress to pay for his wall. Congress isn't going along. They aren't funding anything.
Can you explain how your crazy idea of paying ICE employees while firing "non-essential" workers (like park rangers?) makes any sense? It doesn't even address the problem.
Until Congress passes a funding bill, neither FBI agents or park rangers will be paid. That's the law.