Polymarket traders have committed more than $220 million across about 31,000 equity-linked markets since Polymarket International launched individual-stock markets last October, according to an Allium analysis prepared for Reuters. Nearly 60% of the activity involved contracts tied to individual stock moves, led by Nvidia, Alphabet, Apple and Tesla. The expansion is bringing prediction markets (venues for trading event-based outcomes) into territory traditionally governed by securities rules. Under U.S. law, single-stock contracts are generally treated as security-based swaps, a derivative category overseen by the SEC (U.S. securities regulator) and largely restricted to professional investors. Legal experts say the offshore structure of Polymarket International and limited market protections could make oversight difficult, while regulators are reviewing whether the SEC or CFTC (U.S. derivatives regulator) should take primary responsibility.