A progressive think tank is asking the U.S. Department of Justice (DOJ) to probe the legality of President Donald Trump’s new memecoin.

The president launched the Official Trump (TRUMP) memecoin in mid-January, days before he took office.

The controversial crypto asset rapidly skyrocketed in value and is now the 41st-largest digital asset by market cap.

In a new letter to the DOJ and the Office of Government Ethics, officials at the nonprofit consumer advocacy organization Public Citizen say the memecoin could be a violation of federal law regulating gifts to government officials.

Public Citizen officials point out that the TRUMP website notes the memecoins “are not intended to be, or to be the subject of, an investment opportunity, investment contract, or security of any type.”

“Accordingly, a person sending money for a Trump meme is not purchasing a tangible product. Instead, the person receives only a digital receipt (in a blockchain), which is similar to a donor sending a check and receiving digital confirmation that the check was received…

In short, it appears Trump is not soliciting money in exchange for an investment or tangible product (such as a Bible, sports shoes, or a guitar), but soliciting money in exchange for nothing — that is, asking for a gift that will benefit him personally.

Beyond the issue of solicitation, the Constitution (Article 1, Section 9) forbids accepting money (specifically a ‘present’ or ’emolument’) or anything of value from any ‘king, prince, or foreign state.’ Because of the nature of a cryptocurrency exchange, it is difficult to know whether foreign state actors are gifting the president by way of purchasing a Trump meme.”

Public Citizen officials aren’t the only ones to question the merit of assets like TRUMP. Ethereum (ETH) founder Vitalik Buterin said last month that political coins represented “vehicles for unlimited political bribery,” though he didn’t mention any specific token by name.