In the case of Zahn et al. v. International Paper Co., the U.S. Supreme Court ruled that in a class action lawsuit, each plaintiff must meet federal jurisdictional amount requirements individually for their claims to be heard in federal court, rather than collectively as a group. The plaintiffs were property owners who filed suit against International Paper Company alleging pollution damages to their properties due to discharges from the company's paper mill into Lake Champlain. They sought both injunctive relief and damages exceeding $10,000 per person - which was then the minimum threshold for federal jurisdiction under diversity jurisdiction rules - but some individual claims did not reach this amount when considered separately. The Supreme Court held that even though they had grouped together as a class for legal purposes, each member's claim needed independently to satisfy the monetary requirement for it to fall within federal jurisdiction; otherwise it should be dismissed or remitted back down to state courts where there is no such financial limit on cases being brought before them.

In the dissenting opinion for Zahn et al. v. International Paper Co., Justice Brennan, joined by Justices Douglas and Marshall, argued that the majority's decision was inconsistent with both precedent and the Federal Rules of Civil Procedure. They contended that Rule 23(b)(3) does not require each member of a class action lawsuit to meet federal jurisdictional amount requirements independently; rather it allows aggregation of claims to satisfy this requirement. The dissenting justices believed that this interpretation would better serve judicial economy by preventing multiple lawsuits over common issues. Furthermore, they asserted that Congress intended for class actions to be an efficient way to resolve disputes involving many parties with small individual claims who might otherwise lack resources or incentive to sue individually.