SAN FRANCISCO — Lawyers for the federal government have weighed in against Facebook Inc. in a privacy lawsuit where the company is raising a constitutional challenge to the Telephone Consumer Protection Act.

The TCPA allows private plaintiffs to seek up to $1,500 in statutory damages for each unsolicited robocall or text message they receive, but exempts emergency warnings. Plaintiffs counsel at Lemberg Law filed a class action in March in the Northern District of California claiming that Facebook violated the TCPA by sending unsolicited text messages to people who hadn’t provided their cellphone numbers to the company via its “login notifications” alerts.