If you don’t think it’s fair that billionaires like Donald Trump can run their own self-funded campaigns for president, don’t blame the 2010 Citizens United Supreme Court decision. Blame the 1976 case Buckley v. Valeo instead.

Citizens United lets billionaires give unlimited money to Super PACs trying to elect other people, but billionaires have been able to give as much money as they wanted to their own campaigns since Buckley.

Buckley v. Valeo struck down many provisions of the Federal Election Campaign Act, which was first passed in 1971 and then amended in 1974 after Watergate revealed Richard Nixon’s straightforward corruption. (The quid and the quo were not remotely subtle: The bill of particulars supporting Nixon’s articles of impeachment cited his campaign taking $200,000 from the chairman of McDonald’s, in return for which McDonald’s was allowed to raise the price of a quarter pounder cheeseburger.)

Among the ’70s-era reforms was a $50,000 per calendar year limit on how much of their own money presidential candidates could spend on their campaigns. But since Buckley it’s perfectly fine for candidates to spend as much of their own money as they want. Trump is by no means the first to take advantage of this: Ross Perot spent about $60 million of his own money in his 1992 run for president.

Interestingly, the Supreme Court’s Buckley decision made points that Trump paraphrases today, like this: “The use of personal funds reduces the candidate’s dependence on outside contributions and thereby counteracts the coercive pressures and attendant risks of abuse” of contributions from others.

Trump’s latest filings with the Federal Election Commission show that through this June he’s loaned his campaign $1,804,747.

The Buckley ruling also claimed that rich candidates could be at a disadvantage if they couldn’t spend their own money, because “a candidate’s personal wealth may impede his efforts to persuade others that he needs their financial contributions.” This appears to be the case with Trump, who — despite doing far better in polls than any other Republican candidate — has only received $92,249 in contributions from others through June 30.

While most of the sound and fury about campaign finance laws has focused on Citizens United, reformers recognize the importance of Buckley as well. Twelve major U.S. public interest organizations have released a common campaign finance agenda demanding that the next president appoint Supreme Court justices who will overturn not just Citizens United but also Buckley, and Hillary Clinton recently said, “We have to reverse the effects, not just of Citizens United, but of the Buckley case.”

Correction: August 10, 2015

A previous version of this article incorrectly said that one of Nixon’s articles of impeachment cited bribery involving the price of McDonald’s quarter pounder cheeseburgers; in fact, the bribery was cited as part of the bill of particulars supporting all of the articles of impeachment.