The case of COPE v. COPE in 1890 revolved around a dispute over the validity of a will and testament. The testator, John Cope, had left his estate to his wife for her lifetime use and then to their children upon her death. However, one son contested the will on grounds that it was not properly executed according to Maryland law where the property was located. He argued that there were insufficient witnesses present at its signing as required by state law. The Supreme Court ruled against him stating that since Mr.Cope resided in Pennsylvania when he made his will and died there too, Pennsylvania laws applied which only required two witnesses instead of three as per Maryland's requirement; hence making the execution valid under lex loci actus (law of place where action took place). This ruling established an important precedent regarding jurisdictional issues related to probate matters.

The dissenting opinion in the COPE v. COPE case argued that the majority's decision to uphold a lower court ruling, which allowed a wife to sue her husband for damages resulting from his negligent driving, was incorrect. The dissenters believed this contradicted established legal principles of marital unity and immunity, where one spouse cannot sue another for personal injuries caused by negligence during their marriage. They contended that allowing such lawsuits could potentially disrupt family harmony and open floodgates to frivolous litigation between spouses over minor incidents or accidents within the household. Furthermore, they expressed concern about potential abuses of this new precedent as it might encourage fraudulent claims or collusion between spouses seeking unjust enrichment at the expense of insurance companies.