The Stop Trading on Congressional Knowledge Act became law Wednesday following a White House signing ceremony in the morning. It bans members of Congress, their staff and the executive branch from using non-public information to trade stocks. Southern Minnesota Congressman Tim Walz sponsored the bill, and says he’s been working on it for a long time. He says it took a few years, but is a small step to improve the Union and to help bring transparency back to Congress. Walz was on hand at the White House Wednesday morning when President Obama signed the STOCK Act into law.