Protesters are gathering Saturday in hundreds of cities and towns for a "day of defiance" of the Trump administration. They have a First Amendment right to voice their criticism of the nations policies. But if the protests escalate from speech to violence, President Donald Trump has the constitutional and legal power to use troops to restore basic law and order.Anti-ICE riots in Los Angeles in the last week have put the need for decisive presidential action on full display. Television news has shown scenes of violence that seeks to obstruct the enforcement of federal immigration law. Protesters have launched riots to block and forcibly enter federal buildings, attacked federal officers, and prevented DHS agents from carrying out arrests. They have shut down freeways and blocked traffic. The riots have spread to other cities, such as Austin, Chicago, New York and Denver. Video of the mayhem on TV has shown obvious efforts to stop DHS from apprehending and removing illegal aliens under federal immigration laws.In response, President Donald Trump this week called up 2,000 California National Guardsmen and 700 Marines to Los Angeles. Rather than welcome federal assistance to restore order, Democrat Gov. Gavin Newsom greeted the troops with hostility. He declared the deployment "an illegal act, an immoral act, an unconstitutional act" and accused President Trump of undertaking "the acts of a dictator, not a President," and dared federal authorities to arrest him.FROM RODNEY KING RIOTS TO LA TODAY: WHEN PRESIDENTS HAVE DEPLOYED TROOPS INSIDE THE USContrary to the inflammatory rhetoric of Newsom and other California officials, the initial military deployment rests well within the presidents powers. Trump declared that the mission of the military units is to "temporarily protect" federal agents in Los Angeles "and to protect Federal property, at locations where protests . . . are occurring or are likely to occur based on current threat assessments and planned operations."So far, Los Angeles 2025 has not yet collapsed into the chaos of Los Angeles 1992. The administration today is not replacing the states' responsibility to maintain basic public safety. Instead, Trump is enforcing federal immigration law; in fact, the Supreme Court in Arizona v. United States(2012) has declared that only federal officials may carry out immigration law and policy.The Supreme Court has long recognized the presidential power to use the military to protect federal law enforcement officers carrying out federal law. In In re Neagle (1890), the Supreme Court upheld the use of force by a federal marshal who killed an attacker of a Supreme Court Justice. Even though no law authorized the use of force, the Court ordered the marshal freed:We hold it to be an incontrovertible principle that the government of the United States may, by means of physical force, exercised through its official agents, execute on every foot of American soil the powers and functions that belong to it. This necessarily involves the power to command obedience to its laws, and hence the power to keep the peace.Because of federal supremacy over the matters entrusted to it by the Constitution, the president has the power to protect the security of the officials who carry it out.In the face of nineteenth-century labor strife, the Supreme Court expanded Neagle to include not just the protection of federal personnel, but also their functions.JONATHAN TURLEY: DEMOCRATS' RABID ANTI-ICE RESISTANCE IN LA AGAINST TRUMP COULD BACKFIREIn 1894, union organizers and workers sought to block all trains using Pullman railcars, effectively halting all trains nationwide. President Grover Cleveland ordered U.S. troops to prevent the obstruction of trains carrying the mail. In In re Debs (1895), the Court approved these measures: "The entire strength of the nation may be used to enforce in any part of the land the full and free exercise of all national powers and the security of all rights intrusted by the constitution to its care. The federal government could use even the military, if necessary. "If the emergency arises, the army of the nation, and all its militia, are at the service of the nation, to compel obedience to its laws," Justice Brewer concluded.Congress ratified this authority in Title 10 of the U.S. Code, which authorizes the president to call the National Guard into federal service not just in cases of invasion or rebellion, but also when he "is unable with the regular forces to execute the laws of the United States." This fits within the exceptions to the Posse Comitatus Act, which generally forbids the use of the military to engage in domestic law enforcement except when "expressly authorized by the Constitution or Act of Congress."The presidents use of the military to protect federal personnel and facilities is defensive in nature. Force will only arise if rioters attack. But President Trump has the power to convert this mission from one of defense into actively carrying out immigration law detentions and overcoming obstruction of justice. Congress granted this authority to intervene, even without the agreement of governors, under the Insurrection Act of 1807. For the Act to apply, disorder must rise to the level of an "insurrection" that "opposes or obstructs the execution of the laws of the United States or impedes the course of justice under those laws."CLICK HERE FOR MORE FOX NEWS OPINIONUnder this law, Dwight Eisenhower sent the armed forces into Little Rock when Arkansas Gov. Orville Faubus refused to desegregate the citys public schools. President George H.W. Bush invoked the law, at California Gov. Pete Wilsons request, to send troops to restore order in Los Angeles during the 1992 Rodney King riots. President Trump could invoke the Insurrection Act should disorder spread beyond the attacks on ICE and DHS officers and facilities to a broader collapse of law and order.Critics will suggest that there is a racial motive afoot because Trump is allegedly targeting illegal aliens, their minority communities, and blue inner-cities. But the power to protect the federal government and enforce the law is color blind. Presidents used these same authorities to desegregate southern schools in the 1950s after Brown v. Board of Education and to protect civil rights protesters in the 1960s. Congress originally banned the use of federal troops for law enforcement because of the Souths demand to end the Unions occupation after the Civil War (the end of Reconstruction is one of Washington, D.C.s greatest failures).If critics want the federal government to have the power to enforce civil rights laws against recalcitrant states, they also must concede to President Trump the power to carry out federal immigration laws.If protesters, California officials, and Democratic leaders want to change immigration policy, the answer lies not in obstructing a federal government carrying out an agenda ratified in the last election. Instead, they should rely on the tools bequeathed by the Founders: Congresss authority over funding, legislation, and oversight, the national political system, and, ultimately, elections.CLICK HERE TO READ MORE FROM JOHN YOO