On Monday, after years of speculation, court injunctions, and false starts, the Trump administration will finally put into effect its so-called public charge rule. The new program, which was greenlit by the Supreme Court last month even as it remains tied up in litigation, generally expands the criteria for rejecting visa and green card applicants based on past, present, or expected use of certain government benefits such as Section 8 housing vouchers and Medicaid, among other socioeconomic factors. Like so many other policies to come out of this administration, it is a perfect marriage of antipathy toward the poor and malice toward immigrants.

And because of its unusually long public run-up, we have already been given a small taste of what to expect, which has illuminated both one of the policy’s primary dangers and a key obstacle to assessing its impact: Some people will stop using vital services; others will be deterred before even trying. Immigrant-heavy localities, even without the rule in effect, have already seen widespread disenrollments from a variety of benefits, including those—such as the Special Supplemental Nutrition Program for Women, Infants, and Children, or WIC—that won’t even be impacted by the rule.

To some extent, though, it’s irrelevant who and what kinds of benefits are or aren’t being directly targeted in the rule—that sense of ambiguity is precisely the point. Public charge determinations in the immigration context have existed for over a century and have long been understood to apply to those who were or could become primarily dependent on the government. The new definition is a 200-page blunt-force instrument intended to dissuade millions of people from using basic assistance and health insurance.

“You almost feel like you need a Ph.D. to understand what’s going in and what isn’t, and it’s better to just say, ‘Oh, don’t go there, don’t get a service because they’re going to track you down,’” said Dr. José Pagán, who serves as chairman of the board of New York City’s public Health and Hospitals Corporation in addition to chairing the Department of Public Health Policy and Management at NYU’s School of Global Public Health.

When it was rolled out, the justification from the administration mostly tacked toward preventing the “misuse” of federal funds and was first announced by the White House as “President Donald J. Trump is Ensuring Non-Citizens Do Not Abuse Our Nation’s Public Benefit.” (A racist fiction, but that’s come to be expected at this point.) But as a policy, it belongs less in its purported lane of fiscal responsibility and more in the company of policies like the travel ban: weapons aimed at large swaths of potential legal immigrants and visitors who have been categorically deemed undesirable, whether it’s due to their origin in “shithole countries” or their poverty. Accuracy here isn’t the goal—and indeed isn’t even possible. Travel ban restrictions have gravely impacted U.S. citizens and legal permanent residents across the country. The public charge rule will cast an even wider net. What the Trump administration has done, then, is introduced a potential public health crisis and called it a measure to protect public funds.