A federal judge in North Dakota on Monday temporarily blocked the state's law banning abortions as early as six weeks after fertilization, calling the legislation "clearly unconstitutional."

The preliminary injunction from U.S. District Judge Daniel Hovland means that the nation's most restrictive abortion law, which would bar abortions as soon as a fetal heartbeat is detectable, will not take effect Aug. 1 as planned.

The ruling also suggests that, even as states across the country enact measures limiting abortion access, some of the laws may never take effect because of stiff legal challenges.

Hovland's ruling criticized the North Dakota measure in harsh terms, calling it "clearly unconstitutional under an unbroken stream of United States Supreme Court authority."