In this case the perfect tender rule
b. does not apply.
Step-by-step explanation:
The perfect tender rule has certain exceptions where it cannot be applied to the tender parties and the probates of the tender.
If there is a government ruling against the use of certain products that are necessary for the tender to be completed and the outlaw happens after the tender is signed but before it is completed as a consignment then it cannot be done.
This would come under the ambit of an emergency where the governed ruling makes such deals null and void.