Ask nearly anyone to name President Donald J. Trump’s most significant domestic policy accomplishments. They will likely cite tax legislation and regulatory reform. The first of these was indeed a big policy, one that shifts tax brackets, changes and cuts deductions, and adds an estimated $1.5 trillion to the national deficit over the next ten years. The second of these is, well, not so much. To hear President Trump talk, though, you would think the nation’s rule book has been put on a crash diet. At a White House press event in December, President Trump stood between two piles of papers on the floor: one towering stack supposedly represented regulation today; another tiny stack signified the level of regulation in 1960. He declared that...