Which of the following is NOT an illegal contract at common law?

A. A contract to commit a crime or tort
B. An agreement to solicit for prostitutes
C. A contract to obstruct the administration of justice
D. A contract to supply local goods to a foreign country
E. A contract with an alien enemy during the war

D. A contract to supply local goods to a foreign country

Explanation:
Supplying local goods to a foreign country is not considered illegal under common law unless there is a specific legal prohibition in place. In contrast, contracts involving crimes, torts, or actions obstructing justice are inherently illegal under common law principles.