Supreme Court expected (SEC) to issue rules to provide investors transparency on company donations

"It's part of a continuing effort by the IBT and our allies to crack down on secret corporate political spending, which has become a scourge of U.S. democracy. In the wake of the devastating 2010 Citizens United ruling, the Supreme Court expected the Securities and Exchange Commission (SEC) to issue rules that would give investors transparency on company donations. However, the SEC has refused to act on the matter.
So the unions in the letter said they are now looking for help from the president who has the ability to seek further disclosures from government contractors:
An Executive Order requiring government contractors to disclose their political spending would reach at least 70 percent of the Fortune 100 companies – an important step in shedding light on the millions of dollars influencing our campaigns and elections.
As it stands, at least $600 million in political contributions have been made by nameless donors since 2010. Without proper transparency, voters are left in the dark about the sources and funders of campaign advertising meant to influence voters' choices at the ballot box."

As it stands unions are required to be transparent but not companies for their political donations.

http://teamsternation.blogspot.com/2015/10/unions-ask-obama-to-improve-political.html