President Trump on Friday moved to chisel away at the Obama administration’s legacy on financial regulation, announcing steps to revisit the rules enacted after the 2008 financial crisis and to back away from a measure intended to protect consumers from bad investment advice.

After a White House meeting with executives from Wall Street, Mr. Trump signed a directive aimed at the Dodd-Frank Act, crafted by the Obama administration and passed by Congress in response to the 2008 meltdown. He also signed a memorandum that paves the way for reversing a policy, known as the fiduciary rule, that requires brokers to act in a client’s best interest, rather than seek the highest profits for themselves, when providing retirement advice.

The executive order affecting Dodd-Frank is vague in its wording and expansive in its reach. It never mentions the law by name, instead laying out “core principles” for regulations that include empowering American investors and enhancing the competitiveness of American companies. Even so, it gives the Treasury the authority to restructure major provisions of Dodd-Frank, and it directs the Treasury secretary to make sure existing laws align with administration goals.

Mr. Trump’s action on the fiduciary rule, which Democrats and consumer groups immediately denounced as a gift to Wall Street, could have a more concrete impact. His memorandum directs the Labor Department to review whether the rule may “adversely affect” investors’ ability to access financial advice — and if it does, it authorizes the agency to rescind and revise the rule.