Some said the email was problematic under several laws because, among other things, it linked attendance to donations and encourages employees to solicit contributions.
"It raises issues under the City Charter and, by using the city-supplied email system and city-supplied email addresses, could be construed as a violation, albeit a de minimis one, of the criminal prohibition of the use of public resources to carry on political activity," said Gregory M. Harvey, chair of the public election law practice at Montgomery McCracken Walker & Rhoads.
A lawyer who worked on election law issues for Williams during his last campaign, Samuel C. Stretton, said the email was "wrong."
"It's political macing," said Stretton, an ethics and election lawyer who writes an ethics column for The Legal.
He said the email could implicate both the state Ethics Act as well as the federal Hatch Act, which is enforced by the U.S. Office of Special Counsel.
"An elected official cannot directly solicit campaign contributions from people employed by him in his public office," he said.
He said Williams should "rescind it" and "repudiate it."
Scott A. Coffina, a white-collar defense lawyer at Drinker Biddle & Reath, said there were a number of issues with the email.
"The concern is that there is some element of coercion," he said.
Coffina said there were four key problems with the email as it related to the Hatch Act: Williams was "invoked" by the line "Seth would love if you could attend," it was sent to subordinates, the use of government email and email addresses, and encouraging the employees to pass it on.