• The top Democrat on the House Oversight Committee is investigating whether former President Donald Trump proposed a "quid pro quo" arrangement to oil executives at a dinner in April.
• The probe follows reports that Trump promised to reverse environmental policies in exchange for $1 billion in campaign donations from the oil executives.
• Corporations are prohibited from donating directly to presidential candidates. They can contribute to PACs and their employees' can make private donations, but neither can do so if the donation is intended as a bribe in exchange for favorable treatment.

The House Oversight Committee's top Democrat asked oil executives to reveal whether former President Donald Trump had proposed a "quid-pro-quo" arrangement to them at a recent Florida fundraising dinner, according to letters released Tuesday by Rep. Jamie Raskin, D-Md.

The letters arose from a Washington Post report that Trump hosted the executives for dinner Apr. 11 at his private club, Mar-a-Lago. "You all are wealthy enough," Trump reportedly told the assembled guests. "You should raise $1 billion to return me to the White House."

The former president then reportedly told the oil executives that if they helped him win another term as president, he would reverse the Biden administration's freeze on permits for liquefied natural gas exports, auction more oil drilling leases in the Gulf of Mexico and roll back rules on auto emissions.

The reporting raises "significant potential ethical, campaign finance, and legal issues," Raskin wrote.

The issues "flow from the effective sale of American energy and regulatory policy to commercial interests in return for large campaign contributions," wrote Raskin, who is the ranking Democrat on the Oversight Committee.

Raskin asked the executives to provide descriptions of any discussions related to policy proposals or campaign finance they had at the dinner, as well as any efforts by the CEOs' respective companies to support Trump's campaign.

The letters were sent to Chevron CEO Mike Wirth, ExxonMobil CEO Darren Woods, Continental Resources CEO Robert Lawler, Chesapeake Energy CEO Domenic Dell'Osso, Occidental Petroleum CEO Vicki Hollub, Venture Global CEO Mike Sabel, Cheniere Energy CEO Jack Fusco, EQT CEO Toby Rice and the CEO of major oil lobby American Petroleum Institute (API) Mike Sommers.

The Trump campaign did not immediately respond to CNBC's request for comment on the congressional request.

A spokeswoman for the oil industry group API told CNBC that it, "regularly meets with policymakers and candidates and shares our priorities – the same priorities that we post in detail on our website; in speeches, statements and public events; in regulatory filings and court dockets."

"The meeting last month was no different," API's Andrea Wood said in a statement.

Trump would hardly be the first presidential candidate who made campaign promises to certain groups in order as he asked for donations.

But the wining and dining of executives from just one industry at a candidate's residence, like Mar-a-Lago, raised eyebrows.

Corporations are prohibited from donating directly to presidential candidates. They can contribute to PACs and their employees' can make private donations, but neither can do so if the donation is intended as a bribe in exchange for favorable treatment.

Despite Raskin's demands, and his deadline of May 27 for responses, as long as Republicans hold the House majority there is very little that Raskin can do to force any of the oil execs to turn over information.

Nonetheless, Raskin's decision to demand answers from Trump's dinner guests could potentially benefit his fellow Democrats in a different way.

That's because corporate executives typically go to great lengths to avoid becoming the targets of congressional requests for information.

The prospect of getting caught up in Raskin's inquiry could potentially be enough to make some private sector leaders reconsider whether to accept an invitation to a small, Trump fundraising dinner.