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What if a state department of motor vehicles or a public school insisted that only biological females could use the restroom set aside for females and that biological males had to use the restroom set aside for males?

Would that be a rational policy? Would it be just?

The U.S. Justice Department is now arguing in federal court that such a policy wrongfully discriminates against people whose "gender identity" does not "align" with their biological sex.

The department filed suit on Monday against the State of North Carolina.

At issue is the law North Carolina enacted this year that states: "Public agencies shall require every multiple occupancy bathroom or changing facility to be designated for and only used by persons based on their biological sex."

The law says: "A multiple occupancy bathroom or changing facility may include, but is not limited to, a restroom, locker room, changing room, or shower room."

It defines "biological sex" as the "physical condition of being male or female, which is stated on a person's birth certificate."

In its legal complaint against North Carolina, the Justice Department contested the state's definition of a person's sex and offered an alternative definition.

"An individual's 'sex' consists of multiple factors, which may not always be in alignment," the department said in the complaint.

The complaint then cited various biological factors that might help determine a person's sex, but it capped the list with "gender identity, which is an individual's internal sense of being male or female."

"For individuals who have aspects of their sex that are not in alignment, the person's gender identity is the primary factor in terms of establishing that person's sex," the Justice Department told the court.

Therefore, according to the Justice Department's logic, a person who is biologically male but claims a female "gender identity" must be treated as a female by state governments and schools that receive federal funding.

And that means, according to the Justice Department's logic, that state agencies and schools must allow a person who is biologically male, but who claims a female "gender identity," to use the female facilities.

What about the rights of persons who are biologically female, who identify as female, and who do not want to use the same facilities as biological males?

They do not factor into the Justice Department's argument.

Ultimately, this argument is not only about what is and is not true, but what government may and may not do.

This nation was founded on the correct belief -- even if it did not always live up to it -- that all men are endowed by their Creator with certain unalienable rights and that the basic purpose of government is to protect those rights. The United States justified its independence with an appeal to the Laws of Nature and Nature's God.

But now, progressively, our nation is being ripped loose from its mooring in natural law.

Forty-three years ago, seven members of the Supreme Court declared a "right" to kill an unborn child. Since then, tens of millions of babies have been aborted.

A year ago, five members of the Supreme Court declared a "right" for two people of the same sex to marry. Were there such a right, which there is not, it would mean children do not have a right to a mother -- or a father.

Currently, an eight-member Supreme Court is weighing whether the government can force Christians to act against their faith and cooperate in the distribution of abortifacient drugs that take innocent lives. Thus, could the freedom of conscience be curtailed in the pursuit of further diminishing the right to life.

If the case the Justice Department filed in North Carolina this week makes it to the Supreme Court, the underlying question before the court may be, as it is in the Justice Department's complaint: What is a man and what is a woman?

The laws of nature and nature's God answered that question a long time ago. But President Obama's Justice Department has a different opinion.