Senate Banking Committee Chairman Mike Crapo, R-Idaho, warned the nation’s largest banks Tuesday against cutting off access to gun manufacturers and other controversial industries due to political pressure.

“Banks serve customers who are geographically and politically diverse, and it is wrong to use essential banking services as a way to choke off such services to lawful, creditworthy businesses,” Crapo wrote to the CEOs of Bank of America, Bank of New York Mellon, Citigroup, Goldman Sachs, JPMorgan Chase, Morgan Stanley, State Street Bank, and Wells Fargo.

“I write to express my concern with recent news reports suggesting that large banks may withhold access to credit and services to customers and companies that are operating businesses that comply with federal and state law (and in some cases, are engaged in Constitutionally-protected activities), but are politically disfavored.”

Crapo’s letter is a shot across the bow to both banks and congressional Democrats.

Rep. Maxine Waters, D-Calif., the newly appointed chairwoman of the House Financial Services Committee, and other high-profile Democrats on the panel, including Rep. Alexandria Ocasio-Cortez, D-N.Y., have voiced a desire to push the committee into new political territory like addressing corporate diversity, climate change, and for-profit prisons. All are hot-button issues with progressive activists.

Ocasio-Cortez questioned the CEO of Wells Fargo about his bank’s financing of oil-related projects during his appearance before the committee earlier this month, and Bank of America and JPMorgan reduced or completely cut business with gun manufacturers last year amid national debate over gun control.

“Business lending decisions should be based on creditworthiness, rather than politics or political pressure,” continued Crapo. “Banks were not chartered to manage social policy by limiting credit to politically disfavored industries or promoting credit to politically favored industries.”

Crapo did not add specifics as to what further action he might take if banks began cutting off credit to more businesses, but as chairman of the Senate Banking Committee he has broad oversight and legislative power over the industry.