The Thornburgh v. Abbott case in 1988 was a significant ruling by the U.S. Supreme Court regarding censorship within prisons. The court ruled that prison officials could censor incoming mail if it was deemed necessary for security reasons, even if this meant infringing on inmates' First Amendment rights to free speech and expression. This decision came about after several prisoners and publishers sued the Attorney General of the United States over regulations allowing prison authorities to reject publications they considered detrimental to order, discipline, or security within their institutions. The Supreme Court upheld these regulations with a 5-4 majority vote, arguing that maintaining safety and order in prisons justified some limitations on constitutional protections.

In the dissenting opinion for Thornburgh v. Abbott, Justice Brennan argued that the majority's decision to uphold prison regulations restricting inmates' access to certain publications was a violation of First Amendment rights. He contended that these restrictions were not necessary for maintaining order and security in prisons, as claimed by the majority. Instead, he believed they served only to suppress free expression without any clear justification or compelling state interest. Furthermore, Brennan criticized the court's deference towards prison officials' judgment on this matter and warned against undermining constitutional protections based on administrative convenience or speculative fears about potential disruptions in prisons.