It may turn out that the U.S. Supreme Court’s ruling that the FDA can’t regulate tobacco will affect only that product — or perhaps a few others. But some court observers think that the ruling may signal a historic narrowing of how the justices view federal agencies’ power to regulate anything.

In Food and Drug Administration v. Brown & Williamson Tobacco Corp., No. 98-1152, a 5-4 high court, led by Justice Sandra Day O’Connor, held on March 21 that Congress never gave the FDA the authority to regulate tobacco products.