Key legal question
Whether the taxpayers had standing to appeal to the Federal Tribunal together as spouses
Extracted holding
Yes. Because the spouses were not separated and Swiss tax law provides mutual representation of spouses, X.Z. was deemed to have acted for both spouses throughout the proceedings.
Extracted reasoning
The court inferred joint standing from the marital relationship and the statutory spouse-representation rule, so both spouses were directly affected and had a protected interest.