“[Warren] completely forgets and ignores the fact that lobbying is a First Amendment right,” von Spakovsky told the Washington Free Beacon. “The First Amendment says that you have a right to petition the government for a redress of grievances. That’s what lobbying is, and her idea that it’s somehow evil is just wrong. It’s a basic constitutional right.”

The Warren campaign did not respond to a request for comment.

Other scholars echoed von Spakovsky’s concerns. Michael Barone, a resident fellow at the pro-free market American Enterprise Institute, said he could “see an argument that says this proposal would penalize the exercise of First Amendment rights,” comparing it to “a confiscatory tax on newspaper.” Trevor Burrus, a research fellow for the libertarian Cato Institute’s constitutional studies center, concurred, saying “Sen. Warren has essentially proposed a tax on that fundamental right.” He accused the Democratic presidential hopeful of attempting to “squelch political speech.”

“She pushed for stricter regulations on banks and home loans, and then pushed—’lobbied’ one might say—for the creation of the CFPB,” Burrus said. “In short, Warren apparently believes in lobbying when she does it, or when it is done for causes she believes in. Her lobbying tax proposal would very likely be declared unconstitutional. The Constitution doesn’t permit transparent attempts to squelch political speech.”