On Wednesday, the Supreme Court will hear oral arguments on the biggest abortion rights case in decades. The ruling will determine how far anti-abortion lawmakers can go to restrict the procedure, and whether millions of women in Texas and other states will be able to access abortion without driving hundreds of miles.

Most people haven't heard about the case, according to a new Vox poll — but they also don't support the Texas anti-abortion laws that the Court is deciding whether to uphold.

In light of the new case, Whole Woman's Health v. Hellerstedt, it's worth taking a look at how we got here. Most people know that the Court's 1973 decision in Roe v. Wade legalized abortion in America — but most people don't know about the decisions that came after Roe.

Those decisions weakened Roe and helped launch more than a thousand anti-abortion laws in the states. This new case will test just how much damage those other decisions have done to Roe's protections for women seeking abortion.

How Roe's strong abortion rights protections got weaker

Roe v. Wade held that abortion is a fundamental, constitutional right for women that could only be restricted once a fetus is viable.

But almost immediately, the right to an abortion became contingent on whether a woman could afford to pay for one.

The Court's 1980 decision in Harris v. McRae upheld the Hyde Amendment, which banned federal dollars from funding abortions except in cases of rape, incest, or life endangerment. Those funds include Medicaid, which many low-income women rely on for their health care.

"Roe said you're not supposed to ban abortion," Jessica Mason Pieklo, a constitutional law expert and a senior legal analyst at RH Reality Check, said. "And then Harris v. McRae said, 'We're not banning abortion, we're just making it impossible for poor women to get it.'"

The right to an abortion became contingent on whether a woman could afford to pay for one

Roe also acknowledged that the state has an interest in protecting potential fetal life, at least at a certain point. So the Supreme Court justices set up a legal framework based on the three trimesters of pregnancy.

The Court said states can't interfere with abortion at all during the first trimester, they can regulate abortion only to protect a woman's health during the second, and they can regulate or even ban abortion in the third trimester — as long as they make exceptions for a pregnant woman's life or health.

But 1992's Planned Parenthood v. Casey did away with that framework. Casey said the state has an interest in protecting fetal life at any point during pregnancy, not just after a fetus is viable.

So as long as it didn't present an "undue burden" for a woman seeking an abortion, states could now pass laws regulating abortion for two purposes: protecting potential fetal life, or protecting a woman's health and safety.

It's not possible to protect all fetal life by banning abortion outright, the Casey majority reasoned, because women do still have a right to get an abortion without significant obstacles.

But it is okay to try to convince a woman not to go through with her abortion. The states can pass laws that are "calculated to inform the woman’s free choice, not hinder it."

The Court upheld a Pennsylvania law that required women to wait 24 hours and receive mandatory counseling before having an abortion — but struck down part of the law that forced a woman to inform her husband of the abortion, because abusive partners might interfere with the abortion decisions of domestic violence victims.

"Casey opened the door for a whole host of restrictions that would have probably been unconstitutional under a straight Roe analysis," Pieklo said.

"Casey opened the door for a whole host of restrictions that would have probably been unconstitutional under a straight Roe analysis"

States passed a flurry of waiting periods, mandatory ultrasounds, and "informed consent" counseling laws that sometimes forced doctors to give patients medically inaccurate information about abortion.

The Court said those kinds of laws were fine, because they could theoretically protect fetal life without putting too much of an obstacle in front of women seeking an abortion. (Reproductives rights advocates, of course, argue that it's a pretty big obstacle to force women to make two doctor's appointments when they only need one.)

But by allowing states to regulate abortion to protect a woman's health, the Casey Court opened a critical door for the pro-life movement. Lawmakers could pass regulations that they said were designed to protect women's health — but which, in practice, made it harder for abortion providers to stay open.

How the Supreme Court paved the way for Texas's anti-abortion laws

Two Supreme Court decisions in the mid-2000s really set the legal stage for 2010's Tea Party–aided burst of anti-abortion lawmaking, Pieklo said.

The first is Ayotte v. Planned Parenthood of Northern New England, a 2006 case often forgotten because it is relatively technical. That case did two things that would become relevant to later abortion lawmaking.

First, it allowed courts to strike only the unconstitutional parts of an anti-abortion law without striking the entire law. That helped encourage states to pass omnibus anti-abortion bills with many different provisions — because even if some provisions were struck down, others would stick. Case in point: Only two of the four provisions in Texas's omnibus HB2 are being challenged at the Supreme Court.

Second, Ayotte made it harder for courts to strike down an anti-abortion law on its face — that is, before it can actually go into effect and harm somebody who might later bring suit to try to strike it down. Again, HB2 only made its way to the Supreme Court after Whole Woman's Health, an actual abortion provider, sued the state of Texas for actual harms that providers and their patients said they had suffered.

"Ayotte gives state legislatures the incentive to pass omnibus bills, and then Gonzales gives them the cover to rely on junk science in doing so"

The other case is much more well-known: Gonzales v. Carhart, the 2007 case that upheld the 2003 Partial-Birth Abortion Ban Act.

But in upholding that law, Gonzales also did something else: it gave the court "wide discretion to pass legislation in areas where there is medical and scientific uncertainty."

The medical community isn't at all uncertain about the health benefits or harms of abortion. Abortion is incredibly safe, and claims that it causes breast cancer or mental illness aren't supported by credible medical evidence.

But as the popularity of climate denialism has taught us, it only takes a few doctors or scientists who disagree with the scientific consensus to create the perception of "uncertainty."

"Ayotte gives state legislatures the incentive to pass omnibus bills, and then Gonzales gives them the cover to rely on junk science in doing so," Pieklo said.

Both of these cases, taken together with Casey, are big reasons why the US Fifth Circuit Court of Appeals upheld Texas's HB2.

The law's supporters claim that it protects women's health and safety by better regulating abortion providers. There's good evidence that it doesn't actually do this, and that the lawmakers who passed the law were motivated by banning abortion, not by protecting women's health — which is still a no-no under Casey.

But since the state legislature can basically decide which evidence it finds more convincing, the court may not be able to step in and argue the basic facts or science.

There's still a good constitutional argument for striking down the Texas laws

The current case, Whole Woman's Health v. Hellerstedt, will turn on whether closing clinics, forcing women to wait longer or drive farther, and spend more money constitute an "undue burden" on women's abortion access.

But, Pieklo said, the case will also show us "what the outer limits of that reasoning in Gonzales is — what the court is wiling to dive into and second-guess in terms of the legislature."

Basically, whose proof do we have to accept, and how strong does that proof have to be, in order to determine whether there's an "undue burden"?

Cornell University law professor Michael Dorf argues at SCOTUSblog that even Gonzales's permissive evidentiary standard can't save an abortion restriction that lies about whether it actually protects women's health.

The Casey opinion says, "Unnecessary health regulations that have the purpose or effect of presenting a substantial obstacle to a woman seeking an abortion impose an undue burden on the right."

How does the court know if a regulation is "unnecessary," Dorf asks, unless it takes an objective look at the evidence of what the law will do, and of what the lawmakers intended the law to do when they passed it?

"A law could be a measure designed for the purpose of frustrating access to pre-viability abortion even if it were disguised as a health measure," Dorf writes. "The use of 'unnecessary' and 'purpose' in a single central sentence in Casey thus invites close judicial scrutiny of how ostensible health measures actually function."

That's why Dorf argues that ultimately, the "fundamental right" to an abortion — guaranteed in both Roe and Casey — will win out.