A federal judge says he'll ignore federal sentencing guidelines on the ground they violate the U.S. Constitution's separation of powers.

U.S. District Judge Marvin Shoob, ruling Friday in the case of two people convicted of a December bank robbery, said he intended to sentence them as though their crimes had occurred before November, when the sentencing guidelines went into effect.The guidelines, intended to remedy disparities between the sentences handed down by federal judges across the country, require them to follow a schedule of mandatory sentences.

The guidelines, Shoob ruled, "are not simply guideposts to aid the exercise of judicial discretion. . . . They reduce the role of sentencing judges to filling in the blanks and applying a rigid, mechanical formula."

Shoob said the U.S. Sentencing Commission, which produced the guidelines, was acting "in place of the judge."

He also held unconstitutional the commission itself, required by law to include three federal judges and four non-judiciary members, all appointed by the president.

"Mandatory service of judges on the commission violates the doctrine of separation of powers," Shoob said.

"Constitutional separation of powers," Shoob said, "is so fundamental to our governmental system that every schoolchild learns about our system of checks and balances."

Shoob's ruling was almost certain to be appealed because of the constitutional question it raises.

Shoob also has challenged federal officials over treatment of Cuban refugees jailed in the Atlanta federal penitentiary, saying they were being held unfairly.