Not only does this prevent the millions of people who want to be law-abiding citizens from knowing which laws to abide by, it deprives American voters of the right of self-government through elected representatives that is at the heart of American society. If our votes decide only which candidates get which offices, but not what laws and policies those elected representatives can enact for us to live under, our elections will become more and more like placebos, with the real power being exercised from the judicial bench by people we never voted for.
Liberal judicial activists have been citing laws from countries more to the political left than the United States is, but there is no reason why other judges at other times could not cite very different laws to justify or rationalize decisions that could not be justified or rationalized on the basis of the Constitution of the United States that all judges have sworn to uphold.
In one of Justice Clarence Thomas' opinions, he noted in passing that the distinguished British 18th century legal scholar William Blackstone had said that people condemned to death should be executed within 48 hours. Surely this is not an idea that liberal judicial activists would want to import and Justice Thomas did not rely on it.
But there is no reason in principle why this or any other ideas from abroad should be any less eligible to be imported than the ideas from foreign countries which have already been cherry-picked from an almost endless assortment of possibilities.
The question is not even whether particular foreign laws should become American law. It is not possible for them to become American law, in the sense of rules known in advance, unless they are openly enacted into law by elected officials, rather than imposed by judicial fiat after the fact.