For all of President Trump’s boasts that he is a man of action, he is likely to close out his first 100 days with no major legislation to his credit. That may actually be for the best, since his most significant effort so far would have destroyed the Affordable Care Act.

And yet, even without a big win, Mr. Trump has done significant damage with smaller-bore measures, whose cumulative impact will be felt for a very long time. Specifically, he has signed into law 11 regulatory rollback measures, passed by Republican majorities using the Congressional Review Act — a law that lets lawmakers use fast-track procedures to repeal rules completed in the last six months or so of a previous administration. Two more repeal measures await Mr. Trump’s signature, and 20 that have been introduced in Congress could be passed before fast-track procedures expire. At least there will be no more ugly surprises, since the deadline for introducing new rollback measures under the Congressional Review Act passed on March 30.

The wreckage has been extensive. Some of the regulations already repealed would have strengthened health, safety and fair pay protections for workers. Several others were environmental protections, including a rule, repealed this week, for protecting bears and wolves on federal refuges in Alaska from “predator control” techniques used by the state to accommodate hunters. Mr. Trump has also rolled back broadband privacy protections, antibribery standards for oil companies operating abroad, expanded background checks for mentally ill gun buyers and educational assessment standards for public schools.

Many of the measures that have been introduced but not yet passed by both chambers are environmental protections, including a rule that would limit emissions of methane, a powerful global warming gas, rules and regulations to protect wildlife habitats and endangered species, and safeguards against oil drilling in the Arctic and in national parks.