The statement is TRUE.
The Ethics Reform Act of 1989, guaranteed automatic cost of living adjusments (known as "COLAs") to protect the salaries of judges against inflation. This also applied to other areas of federal employment. Pay raises, however, could be denied if the President declared national emergency or some serious economic crisis were to generate a collapse.
Despite these promises, Congress refused on several occasions throughout the past decades to raise judges' salaries, even on occasions where other federal employees were benefited by COLAs.
This led to a series of court fights that culminated with the authority given to Congress to take away promised pay raises from judges any time before they'd taken formal effect. What this means is that the Constitution will only protect judges’ pay that has been “due and payable". The review of this ruling was denied by the Supreme Court for several years. However, Congress did end up voting to allow an increment of pay for judges later on (but not in 2007 or 2010, to cite some more examples of recent denials).
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