"I hereby certify that the equipment and engine described above has been received by this facility and will be
permanently destroyed for recycling purposes only in accordance with the Heavy-Duty Off-Road Agricultural Equipment Replacement Program Guidelines"
So, at least in CA, it is not legal to export the tractor.
And this is an example Certificate of Destruction: http://valleyair.org/grants/documents/FARMER/Certificate-of-...
"I hereby certify that the equipment and engine described above has been received by this facility and will be permanently destroyed for recycling purposes only in accordance with the Heavy-Duty Off-Road Agricultural Equipment Replacement Program Guidelines"
So, at least in CA, it is not legal to export the tractor.