Eric Thayer/Reuters Elizabeth Warren recently introduced a wealth tax on the top 0.05% of American households. The measure could bring in billions in tax revenue, but faces questions over whether it's constitutional. Insider talked to 7 law professors about these concerns, including 5 who signed a letter in its support. Sen. Elizabeth Warren has made it clear: She wants to tax the ultrawealthy. It's a measure that a majority of Americans support, and could bring in billions in tax revenue, but beyond the political will to make it law it faces several legal obstacles. Besides implementation concerns, it might not be allowed under the Constitution.