A new and unexpected obstacle to President Joe Biden’s green ambitions has emerged: a tiny solar-power company based in San Jose.

Auxin Solar Inc., which accounts for all of 2% of U.S. solar-module manufacturing, recently persuaded the Commerce Department to open a potentially devastating trade inquiry. After the U.S. imposed anti-dumping measures against Chinese solar-cell and module manufacturers just over a decade ago, alternative suppliers sprang up in South Korea and Southeast Asia. Auxin now contends that those other Asian suppliers are effectively used by Chinese companies to circumvent the anti-dumping measures.

If Commerce ultimately agrees, then more than four-fifths of solar-module imports to the U.S. and half of all cells could suddenly be subject to steep tariffs, perhaps levied retroactively. The Solar Energy Industries Association warns of dire consequences for U.S. solar-power development — critical to Biden’s decarbonization targets — claiming that some suppliers are already backing away because of the risk. Heavyweight NextEra Energy Inc. warns that the investigation may delay 2.8 gigawatts of projects slated for this year. Timothy Fox of ClearView Energy Partners, a Washington-based analysis firm, says Commerce’s “structural” inclination toward protectionism may lead it to concur with Auxin.