The Massachusetts state auditor does not have the legal authority to audit the Legislature without consent, Attorney General Andrea Campbell ruled in a decision that strikes a blow to Auditor Diana DiZoglio’s attempt to open state lawmakers’ books.

In a Thursday letter to DiZoglio, Campbell said the conclusion builds on advice given in 1994, when the attorney general’s office “expressed considerable doubt” that the auditor had the authority to audit the Legislature over its objection.

The finding comes after DiZoglio asked Campbell to greenlight a lawsuit against the Legislature in an attempt to get the House and Senate to open up their finances and divulge details on internal proceeds in the face of fierce resistance from top legislative Democrats.

Campbell said she believes in transparency as a cornerstone of good government.

“But that transparency must be achieved through methods that are consistent with the law,” she said in a statement. “After a thorough review of the statutory text, pertinent Supreme Judicial Court decisions, and relevant history, we have concluded that current law does not allow an audit of the Legislature over its objection.”

DiZoglio is still left to pursue the powers to audit the Legislature through a ballot question that could end up before voters if it manages to clear deadlines for signature thresholds this month.

DiZoglio said she respects Campbell’s “right to her opinion, and to defend the position of legislative leaders” as she vowed to continue pushing the ballot question.

“However, a question of statutory interpretation on a matter of such importance to taxpayers, is best answered by the courts, not the executive department of government,” she said in a statement. “Massachusetts has one of the most opaque Legislatures in the nation and this decision reinforces the status quo that benefits powerful insiders while leaving working people in dark.”

Campbell’s office acknowledged the ballot question in their decision, writing state attorneys might have to “whether, and the extent to which, constitutional limitations affect how the law would apply” if the ballot question is successful.

DiZoglio has long pointed to a “historical practice” of the state auditor auditing the Legislature, including more confined reviews from decades ago.

But Campbell said previous reports and audits of legislative activity “do not support the assertion that the (State Auditor’s Office) has authority to undertake a comprehensive audit of the Legislature over the Legislature’s objection.”

“To the contrary, historical precedent indicates that the type of audit now proposed has not previously been performed, and prior state auditors did not believe the (State Auditor’s Office) to have the power now claimed,” Campbell’s office wrote.

Separation of powers principles in the state Constitution may also limit an executive branch entity’s ability to audit certain operations of another branch of government over their objection, Campbell’s office said.

“It is unlikely that the Legislature would have ignored those limitations by granting the auditor broad authority to audit its operations,” Campbell’s office wrote in the Thursday letter.

House Speaker Ronald Mariano and Senate President Karen Spilka applauded the decision.

“The attorney general’s decision has reinforced our long-held position that the auditor does not have the statutory or constitutional authority to audit any other separate branch of government. We are grateful to see the Attorney General’s legal process conclude, and we remain committed to continuing the work of the people of Massachusetts,” the pair said in a statement.