As more companies begin to impose employee vaccine mandates, a legal expert is weighing in on whether Iowa-based companies may be able to do the same. The answer isn't necessarily clear-cut. Denise Hill, an attorney and professor at Drake University's College of Business & Public Administration who recently wrote a book about vaccine mandates, said nothing in federal law prohibits employers from mandating COVID-19 vaccines, but a bill signed by Gov. Kim Reynolds in May makes the picture less clear.House File 889 bans so-called "vaccine passports" and prohibits companies and governments from asking a "customer, patron, client (or) patient" for proof of a COVID-19 vaccination, disqualifying them from receiving state grants or contracts.But the law also extends that prohibition to any "other person who is invited ontothe premises of the business or governmental entity," which Hill says may broaden the law's scope."Certainly some would argue that that means people who are employed," Hill said. "I don't think that at this time, most businesses are considering it to be that way and I think that's an open question."Hill said if the state tried enforcing that, it could bring legal challenges from employers who wish to mandate vaccinations."If the state enforced that, then, at that time, they would have standing to bring a lawsuit to challenge the constitutionality and other provisions of that law," she said. "We are seeing this in other states, and it's inevitable that we're going to see, I think, a large number of them."President Joe Biden recently announced that the White House is considering requiring federal employees to get the COVID-19 vaccine or face rigorous, regular testing. "As a large employer, the largest in this country, who cares about the individuals who keep the government running, we have an obligation to be good stewards of the workforce and ensure their health and their safety," White House Deputy Press Secretary Karine Jean-Pierre said Thursday "We're taking action to protect the federal workforce so that they can continue to execute on the hard and important work of government."Hill said federal workers based in Iowa would not be exempt under state law."Federal employees are, of course, at the federal level and under federalism of the Constitution, that would preempt any state law," Hill said. Hill said a clause in House File 889 that says "Notwithstanding any provision of law to the contrary" is key."Number one, it says that in this situation, yes, the federal government, we recognize (the) federal government," she said. "Number two, if (the state law) were challenged by someone...then this keeps the state law from being overturned on the basis of preemption, so the state did that with purpose, because they don't want it to go down just on that basis, the whole lot."One law that doesn't apply? HIPAA. Despite what many people claim online, Hill said the Health Insurance Portability and Accountability Act doesn't prevent employers from asking for proof of vaccination. The law only applies to "covered entities" — health care providers, plans and clearinghouses.Hill said, ultimately, employers are "trying to do the right thing" amid a testy political environment around vaccines. "I think for employers, trying to incentivize their employees, working to try to educate employees and bringing in people who they rely on, or people even they know, will be most helpful in trying to convince them," she said.