Applied Equipment supplied parts to Litton under a subcontract with a 26% markup. After approving a large tube purchase, Litton secretly negotiated directly with the supplier to bypass Applied and avoid paying the markup. Applied sued for conspiracy to interfere with the contract. California's Supreme Court ruled that a party cannot be sued for conspiracy to interfere with its own contract because conspiracy requires an underlying tort duty—and a contracting party has no duty not to modify or end its own agreements.
You cannot sue your contractor for conspiracy to interfere with your subcontract. The contractor can renegotiate with suppliers or change contract terms without exposing itself to conspiracy liability.