Notable bears in European stock markets are casting doubt on a European regulator's latest proposal on short-selling disclosures following this year's GameStop saga.

EU short-sellers, who have to overcome more regulatory hurdles than their counterparts in other countries, must notify regulators of any short position making up 0.5% or more of a company’s stock. It comes after GameStop shares rocketed over 2,700% earlier this year following a campaign by retail investors to punish those who were short the US video games retailer. Investors caught on the wrong side of the trade, such as Melvin Capital, Point72 and Citron Research, lost millions on their short bets.