Soon after that ruling, said Hedy Weinberg, executive director of the American Civil Liberties Union of Tennessee, the Tennessee General Assembly began the process of amending the state constitution. Early on, because the state legislature leaned more Democratic, these efforts failed, but over time, proponents were able to successfully pass a joint resolution to bring the issue to the polls, where the measure, Amendment 1, was approved by a vote of 52 percent.

Although this constitutional change does not restore any of the abortion restrictions that were previously in place, it's a direct challenge to the court's reasoning in Planned Parenthood:

The provisions of the Tennessee Constitution imply protection of an individual's right to make inherently personal decisions, and to act on those decisions, without government interference. A woman's termination of her pregnancy is just such an inherently intimate and personal enterprise.

According to the pro-amendment "Yes on 1" website, "Since 2000, the primary goal of pro-life Tennesseans has been to overturn this wrong court ruling and restore the ability of citizens and elected officials to decide Tennessee's abortion policies."

Now that the amendment has passed, the General Assembly may have more flexibility to legislate what women must do in order to terminate a pregnancy, including those "resulting from rape or incest." State legislators still can't create statutes that violate federal legal standards on abortion—it can't be outlawed entirely, for example. But they will "almost certainly" have a greater ability to pass restrictions on how and where women get the procedure, said Weinberg—and they plan to, she added.

"Prior to the passage of Amendment 1, it was clear that the Tennessee constitution afforded greater protection to women, in terms of abortion," than the U.S. Constitution, she said. In practice, that has meant the state Supreme Court has had a stricter interpretation of informed-consent laws, mandatory waiting periods, etc., than many federal courts.

At the federal level, the key question has been, "Does this regulation impose an undue burden on a woman seeking an abortion?" said Caroline Corbin, a law professor at the University of Miami. "So far, they've been answering, for the most part, no, on laws about waiting periods, so-called informed-consent laws," and more.

As a result, "there are a lot of statutes that the U.S. has upheld ... that the Tennessee Supreme Court has disagreed," she said. With Tennessee's constitution now fundamentally different, that may no longer be the case. "The job of the court is to interpret the constitution. ... Now, when it's presented with [these laws], it has a different constitution against with to measure it."

Voters in two other states, Colorado and North Dakota, rejected constitutional amendments related to abortion at the polls on Tuesday. But what's happening in Tennessee is part of a broader trend around the country. In Texas, for example, lawmakers passed HB2, which requires doctors who perform abortions to have admitting privileges at hospitals and clinics to meet the same health standards as surgical centers. Although the U.S. Supreme Court temporarily suspended enforcement of that law last month, it may still go into effect.