“Laws are like sausages,” Otto von Bismarck, the 19th century Prussian statesman, is believed to have said. “It is better not to see them being made.”

Big Tech companies operating in the European Union in the 21st century do not have that option. In fact, their activities and how they are regulated are making European law in public on a daily basis—with all the confusion, frustration and financial risk that implies, lawyers say.