Update 2: technology.news has a rather different take than Mann, noting that further legal steps are on their way.

Penn State climate scientist, Michael ‘hockey stick’ Mann commits contempt of court in the ‘climate science trial of the century.’ Prominent alarmist shockingly defies judge and refuses to surrender data for open court examination. Only possible outcome: Mann’s humiliation, defeat and likely criminal investigation in the U.S.

The defendant in the libel trial, the 79-year-old Canadian climatologist, Dr Tim Ball ... is expected to instruct his British Columbia attorneys to trigger mandatory punitive court sanctions, including a ruling that Mann did act with criminal intent when using public funds to commit climate data fraud. Mann’s imminent defeat is set to send shock waves worldwide within the climate science community as the outcome will be both a legal and scientific vindication of U.S. President Donald Trump’s claims that climate scare stories are a “hoax.” (snip)

Michael Mann, who chose to file what many consider to be a cynical SLAPP (Strategic Lawsuit Against Public Participation) libel suit in the British Columbia Supreme Court, Vancouver six long years ago, has astonished legal experts by refusing to comply with the court direction to hand over all his disputed graph’s data. Mann’s iconic hockey stick has been relied upon by the UN’s IPCC and western governments as crucial evidence for the science of ‘man-made global warming.' (snip).

The data wasn't submitted upon court order, because it's a hoax.

If it was legit than it would have been supporting evidence.