That’s a definition of a concept, but not of a factual law. Natural law as defined I arguable by people and not codified or subject to court. I sure as Hell wouldn’t want to enter a courtroom and have the government claim I violated a “natural law”.
When someone claims “natural law” as an offense or defense then I want to see it. Natural law is a concept, an abstract, not a concrete statement of applicable law. Hence, it doesn’t exist.
The first definition in Blacks is correct: Natural law, such as gravity.
LOL! 'It doesn't exist because I say it doesn't' is a pretty sad argument.
The co-author of the citizenship clause of the 14th Amendment, Mr Jacob Howard;
"Every Person born within the limits of the United States, and subject to their jurisdiction, is by virtue of natural law and national law a citizen of the United States. This will not, of course, include persons born in the United States who are foreigners, aliens, who belong to the families of ambassadors or foreign ministers accredited to the Government of the United States, but will include every other class of persons."
http://memory.loc.gov/cgi-bin/ampage?collId=llcg&fileName=073/llcg073.db&recNum=11%20
It seems the Founders as well as subsequent members of Congress thought Natural Law and Natural Rights were a bit more than an 'abstract concept'.