By Robert Romano

The ink has barely dried on President Donald Trump’s executive order denying federal funds to sanctuary cities that refuse to enforce U.S. immigration law, and liberal mayors like New York City’s Bill de Blasio are already promising to sue in federal court to get the federal tax dollars they believe they are entitled to.

“We would be in court immediately to stop it, and I know that will happen in cities across the country,” de Blasio declared. “We are going to fight this. And cities and states all over the country are gonna fight it.”

De Blasio is right. Surely they will. And given the liberal penchant of federal courts at the moment — a slight majority of federal court judges are Democrat appointees — some of those cases may very much slow down Trump’s policy, whether through injunctions or worse, court decisions compelling that federal grants be made in spite of the executive order.

But there is a solution.

Congress could simply defund sanctuary cities that in the determination of the president and Attorney General refuse to enforce U.S. immigration law — bolstering Trump’s policy — in the next continuing resolution due in April.

Then, as a statutory matter, the sanctuary cities would not have much of a leg to stand on in federal court.

This is a teachable moment on the limits of executive action to achieve certain policies.

The same could be said of executive agency rescissions of regulations.

Say, for example, the Trump Environmental Protection Agency (EPA) attempts to rescind the agency’s carbon endangerment finding that finds carbon dioxide to be a harmful pollutant under the terms of the Clean Air Act. And then follows up with attempts to rescind the new and existing coal power plant rules that were based on the finding.

For starters, these rescissions might take a couple of years under the terms of the Administrative Procedures Act.

But, radical environmentalist groups sue in court, falsely claiming that the 2007 Massachusetts v. EPA Supreme Court decision — the basis for the carbon endangerment finding — actually means that carbon dioxide must be treated as a harmful pollutant under the Clean Air Act.

Eventually it works its way up to the Supreme Court again, after a few years, and then suddenly the Supreme Court affirms, creating a requirement that the Clean Air Act be enforced in this way. Guess what happens then? Barring a change of law, the EPA would then be able to do whatever it wanted.

So, why not change the law now? If Congress simply defunds those regulations, then the EPA would have no case whatsoever, since it could not find that Congress’ Article I power of the purse was used unconstitutionally. It wouldn’t even be a justiciable question, it would be a political one with which Congress has discretion.

The same can be said of the whole mess of former Obama administration regulations that Trump and the GOP Congress would like to get rid of. Whether it’s the Department of Housing and Urban Development’s rules conditioning receipt of community development block grants on making changes to local zoning along income and racial guidelines, or the Department of Labor’s persuader rule.

No matter where you look, Congress still has a valuable role to be played to ensure that the massive expansions of federal authority enacted during Obama’s tenure are undone.

On that count, defunding the regulations is great but what would be even better is going after the laws that the regulations were based off of — to prevent them from ever being issued again. The fact is, the true problem of these executive agencies run amuck is not that they were necessarily acting outside of the law, it’s that Congress had given those agencies too much discretion in the first place to issue them.

So, Congress can defund the regulations, or Congress might try defunding the laws they were based on. Or better yet, repeal those laws that give these agencies so much discretion to issue these rules.

Otherwise, don’t be surprised when Trump’s executive orders defunding sanctuary cities and other executive action get tied up in court for years, and the parts of the president’s agenda remains unimplemented. But with Congress exercising its Article I powers, including the power of the purse, that agenda will become bulletproof.

Robert Romano is the senior editor of Americans for Limited Government.