Donald Trump rallies are known to draw a large crowd of supporters and protestors — but a little known law supported by President Obama in 2012 demands Secret Service stop protests among any of the officials they’re charged to protect. Slate writer Dahlia Lithwick reported back in 2012 that President Obama signed an anti-protest bill into law prohibiting anyone from “knowingly… impede or disrupt the orderly conduct of Government business or official functions” in locations guarded by the Secret Service. That includes speeches made by the Republican frontrunner and former First Lady Hillary Clinton, who has Secret Service protection for...