An executive order by President Donald Trump hasn’t stopped the IRS from enforcing the Obamacare mandate that requires certain employers to offer health coverage to workers.

And now several employer groups, including the ERISA Industry Committee and the National Federation of Independent Business, are asking the IRS to back off on enforcing the Affordable Care Act’s employer mandate. By continuing to assess penalties under the ACA, the groups say, the IRS is violating Obamacare and isn’t complying with Trump’s executive order that instructed agencies to minimize the health-care law’s economic and regulatory impact pending its repeal.

It can be costly...