In his first term, President Trump seemed to relish ripping through the norms and standards of self-restraint that his predecessors had respected. Three weeks into his second term, hand-wringing about norms seems quaint.

Other presidents have occasionally ignored or claimed a right to bypass particular statutes. But Mr. Trump has opened the throttle on defying legal limits.

“We are well past euphemism about ‘pushing the limits,’ ‘stretching the envelope’ and the like,” said Peter M. Shane, who is a legal scholar in residence at New York University and the author of a casebook on separation-of-powers law. The array of legal constraints Mr. Trump has violated, Mr. Shane added, amounts to “programmatic sabotage and rampant lawlessness.”

Mr. Trump has effectively nullified laws, such as by ordering the Justice Department to refrain from enforcing a ban on the wildly popular app TikTok and by blocking migrants from invoking a statute allowing them to request asylum. He moved to effectively shutter a federal agency Congress created and tried to freeze congressionally approved spending, including most foreign aid. He summarily fired prosecutors, inspectors general and board members of independent agencies in defiance of legal rules against arbitrary removal.

More than two dozen lawsuits have been filed so far challenging moves by the Trump administration, though many overlap: At least nine, for example, concern his bid to change the constitutional understanding that babies born on U.S. soil to undocumented parents are citizens.