Congressional Democrats are continuing to gather ideas for limiting corporate involvement in elections as they prepare legislation responding to last month’s U.S. Supreme Court decision in Citizens United v. FEC (pdf).

Harvard Law Professor Laurence Tribe, headlining a hearing before a House Judiciary subcommittee, laid out a slew of proposals he thinks Congress should take up. They include requiring shareholder preapproval for corporate spending, limiting spending by federal government contractors, and allowing states to pass laws prohibiting spending by out-of-state corporations.