President Donald Trump’s lawyers on Thursday filed a lawsuit against an accounting firm and Manhattan District Attorney Cyrus R. Vance Jr. over attempts to gain access to the president’s personal and corporate tax returns.

Vance recently subpoenaed Trump’s accounting firm Mazars USA, demanding eight years of tax returns from both Trump and the Trump Organization.

The firm signaled that it would comply with Vance’s subpoena, stating that it “will respect the legal process and fully comply with its legal obligations.”

“We believe strongly in the ethical and professional rules and regulations that govern our industry, our work and our client interactions,” the firm continued. “As a matter of firm policy and professional rules we do not comment on the work we conduct for our clients.”

The president’s lawyers filed a lawsuit to combat Vance’s efforts in the U.S. District Court in New York on Thursday, citing “significant constitutional issues.”

“In response to the subpoenas issued by the New York County District Attorney, we have filed a lawsuit this morning in Federal Court on behalf of the President in order to address the significant constitutional issues at stake in this case,” Trump’s lawyer Jay Sekulow said in a statement Thursday.

Vance’s office issued the subpoena to the Trump Organization as part of an investigation into the $130,000 “hush-money” payment former Trump lawyer Michael Cohen made to porn star Stormy Daniels, who professed to have had an affair with the president — a claim that Trump has repeatedly denied.

Neither Vance’s office nor Trump’s accounting firm has issued a comment, according to the Associated Press.