Scrutiny on semiconductor supply chains has not been limited to the Executive Branch, however, and a recent request from Congress illustrates how even individual transactions involving specific links in the semiconductor supply may become subject to regulatory action as Commerce and other U.S. agencies develop a deeper understanding of supply chain dynamics. On March 19, 2021, two Republican lawmakers sent a letter to the Commerce Secretary to prevent ASML Holdings NV, a Dutch technology firm, from supplying critical systems to Semiconductor Manufacturing International Corp. ("SMIC"), a Chinese chipmaker. Sen. Marco Rubio (R-FL) and Rep. Michael McCaul (R-Texas) said that the U.S. should exercise its diplomatic leverage to weaken China's foothold in the semiconductor industry. The lawmakers also asked Commerce Secretary Raimondo to add SMIC to the Commerce Department's Entity List, which would limit SMIC's ability to source materials even for those that are not manufactured in the United States.