The U.S. Constitution gives Congress the power to write laws regulating commerce and financial markets — including interest-rate limits on credit cards. Trump has called for a one-year cap at 10%, but no such law currently exists, and a presidential proclamation alone doesn’t change private-sector interest rates.

U.S. President Donald Trump's executive order restricting Wall Street investors from buying up single-family homes could ​boost demand for homes while doing little to address tight housing supply, a k...