Certainly an interesting proposal, but is it constitutional? In light of the Supreme Court's Citizens United decision that "money is speech" and the First Amendment right to petition the government for a “redress of grievances.” This applied to campaign contributions and independent expenditures, but the same case could be made for lobbying expenditures. Elizabeth Warren’s lobby tax may not hold up to legal scrutiny I can also see all kinds of loopholes with the 501(c)(3) and (c)(4) organizations that would be exempt from the tax as opposed to the 501(c)(6) that would be subject to the tax. I spent nine months lobbying for a public interest group (took 10 years off my life!) where my time for payroll purposes was split between the organization's (c)(3) educational functions and (c)(4) advocacy functions. (if its Tuesday, I must be doing research and not lobbying). It would probably not be difficult for a trade association to flip its (c)(6) to exempt status. A former assistant of mine is now the chief lobbyist for Hershey Foods (the issues are tariffs, trade agreements, product labeling, agricultural subsidies....). Another work around or loophole for companies like Hershey would be to assign their lobbyists as contractors to a trade association that might have (c)(4) status (e.g. National Confectioners Association that represents candy/chocolate companies). But I applaud Warren for the effort and would love to see any serious lobbying reform that could withstand a constitutional test in a conservative Supreme Court.