Public companies in the US are supposed to follow accounting standards established by the Financial Accounting Standards Board (FASB) when publishing financial statements. These standards require that assets be valued at current market rates.
During the 2008 financial crisis, banks pressured Congress to pass legislation to suspend mark-to-market accounting since many banks were holding assets that had severely dropped in value after the crisis. Congress passed the Emergency Economic Stabilization Act (EESA) which required the Securities and Exchange Commission (SEC) to examine "Alternative accounting standards to those provided in [Financial Accounting Standards Board] Statement Number 157".
At the time the SEC decided not to suspend mark-to-market. However, the EESA reaffirmed that the SEC has the authority to suspend mark-to-market if they choose.