Is money earned from working in a company, while violating a contract clause prohibiting marriage to a foreigner, entirely unlawful (haram), partially unlawful, or not unlawful at all? And is the condition nullified by divorcing the wife, or does it remain breached?

Every condition that benefits one of the contracting parties must be fulfilled, based on the Almighty’s saying: "O you who have believed, fulfill [all] contracts," and the Prophet’s (peace be upon him) saying: "Muslims are bound by their conditions."

If the company has a legitimate reason for stipulating that condition, and it was accepted, and the contract was made upon it, then it is obligatory to fulfill it. Violating the condition is a sin, but it does not make the salary unlawful as long as the work has been performed.

As for the wife, it is not advisable to divorce her. Instead, one should seek to be released from the company's terms and ask for their forgiveness regarding the condition, as divorcing her might not cancel the condition.