On Twitter, President Donald Trump said he would be "using the power of the pen to give great HealthCare to many people − FAST." He isn't bluffing. His White House has been working on a series of executive actions on health insurance.

But his tweet is misleading. The most far-reaching action under consideration would not give anyone health care. Rather, it would dramatically reduce enforcement of Obamacare's fines on people without insurance.

If he takes this action, Trump will be following in Barack Obama's footsteps. In December 2013, President Obama had a problem. The regulations imposed by his health-care law were causing some insurance plans to be canceled. But the new Obamacare website was not working well, and people with canceled plans were having trouble buying new ones. Without insurance, they could be fined.

So the Obama administration granted a "hardship exemption" under the law to anyone with a canceled plan. As liberal commentator Ezra Klein put it at the time, it decided that "Obamacare itself is the hardship." The Trump administration may decide to grant hardship exemptions even more liberally.

I have written against Obamacare's "individual mandate" fines many, many times. I urged the Supreme Court to strike down the original version of the mandate. When the court instead modified the mandate, I argued that Congress should replace Obamacare with a health system less reliant on coercing people to buy insurance they do not want.

Yet I don't think the executive branch should just stop enforcing the fines, for three reasons.

First: The fines are in the law. Whether we like it or not, Congress passed a law that includes these fines and the president signed it. Obama abused the law by stretching the provision for hardship exemptions, as law professor Josh Blackman has explained.

The Trump administration has rightly criticized its predecessor for rewriting laws it was supposed to enforce. It should not now imitate the Obama administration's worst practices. Trump's tweet even used the same objectionable rhetoric Obama employed: Congress has failed to write the law he wants, so he will act without its authorization.

Second: Refusing to enforce the fines would destabilize insurance markets. The fines are in the law to make its protection for people with pre-existing conditions workable. Obamacare requires insurers to treat the sick and the healthy the same. Without the fines, healthy people might go without insurance until they get sick. But if enough people follow that course, premiums will spike − and other healthy people will then leave the market.

A law to repeal and replace Obamacare could end the fines, while including other provisions to keep insurance markets from unraveling. The protections for people with pre-existing conditions could be modified; other incentives to buy insurance could be provided. But if you just stop enforcing the fines, people in the individual market will face higher premiums. More insurers could exit the exchanges.

Third: Congress has just rejected this specific policy. The Senate considered a "skinny repeal" bill this summer that primarily consisted of abolishing the fines. It could not get 50 votes − and some senators who endorsed it did so while expressing hope that the bill would be modified before becoming law. They wanted it modified because they did not want to see the end of the fines lead to higher premiums.

Where the Affordable Care Act genuinely gives the executive branch leeway, the Trump administration should exercise its discretion to loosen restrictions on markets in a well-considered way. Reading the fines out of the law doesn't meet any part of that description. The administration should shelve this idea.

Ramesh Ponnuru is a Bloomberg View columnist. He is a senior editor of National Review.