WASHINGTON — In a pair of decisions issued on Tuesday, the Supreme Court made it easier to import textbooks and other copyrighted products from abroad and made it harder for plaintiffs in class-action suits to stay out of federal court.

The copyright case, Kirtsaeng v. John Wiley & Sons, No. 11-697, arose from the activities of a Thai student who attended Cornell University and the University of Southern California. The student, Supap Kirtsaeng, helped pay for his education by selling textbooks that his friends and relatives had bought in Thailand at low prices and shipped to him.

A publisher of some of the textbooks, John Wiley & Sons, sued Mr. Kirtsaeng for copyright infringement, and it won $600,000 in the lower courts. In a 6-to-3 decision, the Supreme Court threw out that award and ruled that imported copyrighted goods were subject to the same rules as goods bought in the United States: owners of particular copies can do what they like with them.

In legal jargon, the court applied the first-sale doctrine to copyrighted materials from abroad. Under that doctrine, buyers of books, records and other copyrighted goods may lend or sell them as they wish.