“Which takes precedence? The contracts or this executive whim?”
Govt. can cancel contracts pretty much any time it wants.
““Which takes precedence? The contracts or this executive whim?””
The President has the authority to halt work or terminate contracts for the convenience of the Government. The Government is responsible to compensate Contractors for all reasonable costs incurred.
The US Army Corps of Engineers, who are the Contracting Activity for all of the Border Wall Projects, has confirmed that all of the contracts include the standard clause, allowing for termination for the convenience of the Government.