The biggest banks are traditionally the most cautious. But Wells Fargo’s scrutiny of Ms. Fried’s political beliefs set its decision apart.

“If a bank is going to start drawing a line based on a candidate’s particular advocacy, where does a bank draw that line?” asked Christian Bax, who until Aug. 10 was Florida’s medical marijuana director. “Is it going to extend to every candidate in Florida who advocates for medical marijuana?”

A Wells Fargo spokeswoman declined to discuss Ms. Fried’s case specifically, but said the bank has a policy of avoiding the marijuana industry.

“It is Wells Fargo’s policy not to knowingly bank or provide services to marijuana businesses or for activities related to those businesses, based on federal laws under which the sale and use of marijuana is illegal even if state laws differ,” the spokeswoman, Bridget Braxton, said in a statement. “We continually review our banking relationships to ensure we adhere to strict regulatory and risk guidelines.”

Erik Gordon, assistant professor at University of Michigan’s Ross School of Business, said that while it was highly unlikely that Ms. Fried could successfully claim Wells Fargo had impeded her right to free speech, the bank’s move seemed to him “like semi-paranoid overkill.”

“They’re seeing the word ‘marijuana’ — they’re seeing a word that could indicate danger — and are assuming that the danger exists without thinking carefully about what’s going on,” he said.

Banks have gotten mixed signals about marijuana from the federal government. In 2013, the Justice Department announced that it would not commit resources to prosecuting legitimate marijuana businesses and would instead focus on things like breaking up drug-trafficking rings and preventing the sale of marijuana to children. But the Trump administration rescinded that guidance in January, saying prosecutors should use their discretion to prosecute marijuana-related cases just as they would for any other category of offenses.