UNITED NATIONS — More than 20 world leaders tendered legal documents on Wednesday, formally binding their governments to the Paris climate accord at a General Assembly ceremony here and all but ensuring that the agreement will go into force by the end of the year.

The specifics of each country’s plans, though, are voluntary. There are no sanctions for failing to control pollution or to put economic polices into practice, or for submitting unambitious pledges.

The legally binding portion of the Paris accord does little more than require governments to continue to convene at high-profile global climate summit meetings, make public pledges to tackle global warming at home and submit those plans to be published on a United Nations website.

The ultimate importance of the climate accord will be determined by its members.

“If enough countries start implementing the Paris agreement, historians will see this as a watershed moment,” said Erik Solheim, director of the United Nations environment program. “But if we don’t implement it, this will just be bringing a bunch of politicians together around a piece of paper.”