Copyright Getty Images Photo by: Scott Olson PRINCETON, Mo. — An ordinance approved this week in a northern Missouri county would allow local deputies to arrest federal agents who are enforcing certain gun laws. The "Mercer County Missouri Second Amendment Preservation Act" approved Monday by the county commission also seeks to nullify federal gun laws and regulations that have a "chilling effect" on firearm ownership, The St. Joseph News-Press reported [newspressnow.com] . The ordinance, which took effect Tuesday, includes an exception for Mercer County deputies who help federal agents arrest suspected criminals. Earlier this month, the Missouri House advanced a proposed law [apnews.com] that would ban local police officers from enforcing federal gun laws, including using federal laws to take away people’s guns. Royce de R. Barondes, a University of Missouri law professor, said under the U.S. Constitution, counties do not have the legal authority to nullify federal laws. He said federal officers have immunity from criminal liability if they are discharging their duties. John Ham, spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the ATF doesn’t comment on local ordinances. A spokesperson for the FBI referred the News-Press to the ATF. County commissioners and county law enforcement authorities either declined or were not available for interviews, the News-Press reported.