Short-sellers around the globe will be unmasked starting on Friday as new European rules come into effect.
The European Securities and Markets Authority (ESMA), the EU regulator, has issued new rules on the short-selling of securities indicating that anyone with short positions of greater than 0.2 percent in an EU company's shares must report it to regulators.
Positions of more than 0.5 percent will be publicly released, naming both the company and the short-seller. Public disclosure is triggered any time that level is hit with each 0.1 percent increase or decrease after that.
Teams of lawyers were working into the night to help banks, hedge funds and other investors comply with the rules with the deadline due at 3:30 p.m. local time in each jurisdiction.
And disclosures need to be filed separately to each national regulator which has introduced plenty of headaches, given that in some countries, like Hungary, the paperwork is largely written in the local language.
Sources from the finance industry have indicated to CNBC that the disclosure rules will hurt overall market activity in Europe, potentially driving investors to other markets like Hong Kong
Others have told CNBC that a version of the rule already in place in Spain and Portugal hasn't had a major impact.
Still, it is a major step towards unmasking the short positions of hedge funds which are typically one of their most closely guarded secrets.
And any pushback from the U.S. will yet again pit European regulators against their American counterparts.