Massachusetts' top insurance official said Monday that the state won't allow consumers to keep health insurance policies that fall below the minimum requirements of the federal health care law. State Insurance Commissioner Joseph Murphy said in a letter sent Monday to the Obama administration that substandard insurance policies are "virtually non-existent" in Massachusetts because of its first-in-the-nation health care law that took effect in 2007. In a reversal of policy, Obama announced last week that millions of Americans would be allowed to renew individual coverage plans that otherwise would be cancelled under the federal law in 2014.