subject to challenge =?

Context:

Harvard had been pummelled in the press for its reticence, but it is
common and sometimes necessary for universities to sit on the results
of internal misconduct investigations. This is particularly true when
the case is complex — as they often are — and the findings subject to
challenge, or when other researchers have been implicated. Indeed, the
US Office of Research Integrity (ORI), which monitors investigations
of researchers who are funded by the National Institutes of Health, asks
institutions not to make their investigations public until the ORI has
completed its own assessment. This can delay a verdict for weeks or
even years after the university completes its own investigation.