A federal judge in Texas on Friday ordered the FDA to temporarily halt approval of the drug mifepristone for abortion.

The ruling, which is not expected to take effect immediately, came in a lawsuit by an anti-abortion group claiming the FDA approved the drug 23 years ago without adequate evidence of safety.

The ruling comes as other legal disputes about the abortion medication are happening across the country. In January, for example, abortion rights supporters filed separate lawsuits challenging abortion pill restrictions imposed in North Carolina and West Virginia. In Georgia, lawmakers have so far failed to win legislation that would ban the medication from being sent through the mail.

Legal experts foresee years of court battles over access to the pills.

Here’s a closer look at the issue.

What is mifepristone?

The U.S. Food and Drug Administration approved mifepristone in 2000 to end pregnancy, when used in combination with a second drug, misoprostol. The combination is approved for use up to the 10th week of pregnancy.

Mifepristone is taken first to dilate the cervix and block a hormone needed to sustain a pregnancy. Misoprostol is taken a day or two later, causing contractions to empty the uterus.

More than half of U.S. abortions are now done with pills rather than with a procedure, according to the Guttmacher Institute, a research group that supports abortion rights. In rare cases, the drug combination can cause excess bleeding, requiring emergency care.