Efforts by U.S. antitrust regulators to break up Alphabet by forcing a sale of its Google Chrome browser and other proposals to limit its search dominance are likely to run into legal challenges on grounds the remedies are extreme.

After a ruling in August that Google illegally monopolized the search market, U.S. Department of Justice prosecutors argued to a judge on Wednesday that the company must sell Chrome, share data and search results with rivals and possibly sell its Android smartphone software.

Alphabet shares closed nearly 5% lower on Thursday. The proposals are part of a landmark case aimed at reshaping how users find information. But a new pro-business administration of President-elect Donald Trump next year could change that effort and legal proceedings could last years, experts said.