WASHINGTON - US House of Representatives Speaker Paul Ryan said on Thursday lawmakers should close any possible legal gaps that may allow the mentally ill to obtain guns, as the country reeled from a school shooting that killed 17 and a year after Congress ended expanded background checks tied to mental health problems."As you know mental health is often a big problem underlying these tragedies," he told reporters. "We want to make sure that if someone is in the mental health system that they do not get a gun if they should not have a gun."Last year, Congress passed a resolution that eliminated expanded background checks for gun purchasers receiving Social Security benefits for a mental impairment, which Republican lawmakers had said deprived the mentally ill of their gun rights. Because the resolution, signed by President Donald Trump on February 28, 2017, was passed under the Congressional Review Act regulators can never enact similar requirements in the future.