In terms of determining substantive issues in a case without federal law, what factors must a federal judge consider?

The correct answer focuses on factors that help maintain the balance between state and federal systems, especially when federal law is not involved in a case. In this context, a federal judge must examine whether a state law issue is outcome determinative, meaning that the ruling could significantly affect the outcome of the case, potentially altering the rights of the parties involved.

The balance of interests entails weighing the respective interests of the states and federal interests in matters where state law governs. This is crucial to ensuring that the federal court does not inadvertently create an imbalance that favors litigants in one jurisdiction over another, which would undermine the principles of federalism.

Avoidance of forum shopping addresses the concern where parties may seek to gain unfair advantages by selecting jurisdictions that might favor their case. In other words, federal courts must be careful to apply state law principles while preventing parties from manipulating the system in search of a more favorable legal environment.

Together, these factors ensure that federal courts respect and appropriately apply state law while maintaining a fair judicial process. The other options do not align with the fundamental concerns of a federal court determining substantive issues in cases without federal law.