Startup companies that celebrated the passage of a U.S. law allowing them to solicit investors more more openly say regulators may undercut that move by requiring detailed disclosures of their fundraising.

An 80-year-old ban on advertising private investments ends today, allowing businesses to make public pitches to certain investors. At the same time, the Securities and Exchange Commission is weighing whether to require companies to file advance disclosures of those efforts. Failing to file could trigger a one-year disqualification from selling shares.

Startups say the SEC's proposal was written with more established companies in mind. The cycle of fundraising at younger companies can be less predictable, relying on chance introductions and pitches at meetings of investors known as demo days.