In the case of DuPont v. Commissioner of Internal Revenue, 1932, the U.S Supreme Court was tasked with determining whether or not a taxpayer could deduct interest on loans used to purchase tax-exempt securities. The petitioner, E.I du Pont de Nemours & Company (DuPont), had borrowed money to buy such securities and claimed deductions for the loan interests paid in its income tax returns. However, these claims were denied by the Commissioner of Internal Revenue who argued that allowing such deductions would essentially make taxable income out of what Congress intended to be exempt from taxation. The court ruled in favor of DuPont stating that there is no provision in law which disallows deduction based on how borrowed funds are utilized by a taxpayer. It further clarified that while Congress has power to limit or condition this right under law, it hadn't done so at this point and hence taxpayers have full liberty over their financial decisions without any fear about possible loss through denial of standard deductions.

In the dissenting opinion for DuPont v. Commissioner of Internal Revenue, it was argued that the majority's decision to allow E.I. du Pont de Nemours & Company to deduct dividends received from its wholly-owned Canadian subsidiary as business expenses was incorrect. The dissenting justices believed this interpretation contradicted both the letter and spirit of tax law at that time, which only allowed deductions for ordinary and necessary business expenses. They contended that these dividends were not a cost of doing business but rather a return on investment, thus should be treated as income rather than an expense deductible against other income sources. This distinction is crucial because treating such dividends as deductible expenses significantly reduces taxable income and therefore tax liability – an outcome they deemed unfair and contrary to legislative intent.