WASHINGTON — The Supreme Court ruling in the Environmental Protection Agency case on Thursday was a substantial victory for libertarian-minded conservatives who have worked for decades to curtail or dismantle modern-style government regulation of the economy.

In striking down an E.P.A. plan to reduce carbon emissions from power plants, the court issued a decision whose implications go beyond hobbling the government’s ability to fight climate change. Many other types of regulations might now be harder to defend.

The ruling widens an opening to attack a government structure that, in the 20th century, became the way American society imposes rules on businesses: Agencies set up by Congress come up with the specific methods of ensuring that the air and water are clean, that food, drugs, vehicles and consumer products are safe, and that financial firms follow the rules.