The U.S. Supreme Court is debating the legal definition of marriage this week, while the state of North Dakota is pushing through legislation designed to nibble away at one of the body's landmark rulings.

That was the 1973 decision in Roe. V. Wade which made abortion legal in the United States.

The most controversial new measure is an amendment to the state constitution which protects life at any stage of development.

It passed the North Dakota legislature last week and will become law there if voters approve the amendment when it goes on the ballot in 2014.

The North Dakota personhood amendment is the first such initiative that has been passed in the United States.

The amendment is one of many proposed around the U.S. It seeks to establish "personhood" for the unborn.

Mississippi and Colorado have already defeated similar amendments.

The catalyst for the personhood movement is a group called Personhood USA, a Christian lobbying organization.

Its ultimate goal, according to the group's website, is to amend the U.S. constitution so that it recognizes that humans are persons from the beginning of their biological development, without exceptions.

Two-thirds of the states must approve an amendment to the U.S. Constitution.

The personhood movement has been criticized by pro-life groups on strategic grounds.

Eagle Forum, a pro-life organization that has opposed abortion since 1972, claims that the Colorado personhood initiative was poorly designed and unpopular.

They also say that the personhood measures cause the defeat of pro-life candidates whose names appear alongside them on the ballot.

On the other hand, the Christian organization Focus on the Family, another vocal opponent of abortion based in Colorado, supported the personhood effort there.

Personhood USA noted in a press release issued when the North Dakota amendment passed that every pro-life organization in the state supports the state's personhood amendment.

Personhood initiatives are not limited to the United States. LifeSiteNews.com reported last year that the Vatican had launched a petition drive in Europe to gain support for a personhood effort in the European Union.

However, Catholic bishops in the United States have opposed efforts to pass personhood legislation. They believe the measures are too extreme to gain popular support.

The personhood amendment is not the only legislation aimed at restricting abortion in North Dakota. The state's governor signed three bills on Tuesday which also limit the procedure.

One prevents abortions if a fetal heartbeat is detectable.

Another law requires that doctors performing abortions have admitting privileges at a local hospital. The third forbids abortions on the basis of genetic defects or genetic selection.

Whether or not the new laws will hold up to a court challenge is debatable.

Even so, North Dakota governor Jack Dalrymple believes the measures will serve a purpose.

"Although the likelihood of this measure surviving a court challenge remains in question, this bill is a legitimate attempt by state legislature to discover the boundaries of Roe v. Wade," he said.