U.S. Attorney General Jeff Sessions on Thursday barred immigration judges from a once-common practice of shelving deportation cases involving some immigrants with deep ties to the United States.

The practice, known as administrative closure, allowed judges to clear low-priority cases off their dockets, effectively letting some immigrants remain indefinitely in the United States despite their lack of legal status.

Under President Barack Obama there had been an effort to administratively close certain cases as a way of allowing judges to focus on higher-priority matters and reduce the immigration court backlog. More than 200,000 cases were closed during the last six years of his presidency.