Three business partners sued a Chinese company for backing out of an agreement to build a manufacturing plant in Iran. The court ruled the contract was illegal and unenforceable because it violated U.S. federal sanctions laws prohibiting transactions with Iran. The partners lost their case and couldn't recover their money or lost profits. This matters to subcontractors because contracts involving sanctioned countries are void—you can't enforce them even if you've already spent money on the project.
Never sign contracts involving sanctioned countries (Iran, North Korea, Syria, etc.) without explicit U.S. government approval. They're unenforceable and you'll lose your investment.