According to the Associated Press, Judge Paul Boggs said that the operator refused to take on 85 workers from the former Cannelton mine in Kanawha County, West Virginia.
The mine was purchased from bankrupt Horizon Natural Resources and reopened by Massey as a non-union mine under Mammoth Resources.
The move was made, Boggs said, so that the company would not have to heed the regulations of the United Mine Workers of America and proceed with contract negotiations for the mine. The mine was union operated since at least the 1970s, the news service said.
Massey said the crews were not hired because it had secured more qualified employees, and that it was exempt from union bargaining because Mammoth was not a legal Horizon successor.
According to the AP the judge rejected the operator's stance, arguing that the mine was run in the same manner and there was evidence Massey wanted to discourage union activity and UMWA bargaining.
Boggs' recommendations include plans for the operator to offer positions to the former Cannelton workers and provide back pay, as well as recognition of and bargaining with the union.
Massey said in a statement late Monday that it disagrees with the decision and will begin steps to challenge it.
"These recommendations are neither binding nor final," said Massey spokesman Jeff Gillenwater.
"Mammoth Coal Company disagrees with the ALJ's [administrative law judge's] recommendations and will respond to the National Labor Relations Board accordingly."
It has 30 days to do so before the decision becomes final, the AP said.
The UMWA made a statement on the decision Monday, calling it a "tremendous victory" for its members.
"It demonstrates that the actions Massey Energy took in the wake of the bankruptcy of Horizon Natural Resources were not just wrong, they were so outside the bounds of law and decency that they must be corrected immediately," said president Cecil Roberts.
"We've said all along that what the company did to the workers at Cannelton was illegal.
"We're extremely gratified that the NLRB law judge who heard all the evidence agrees with us, and we look forward to the day, hopefully very soon, when our members can walk back into that mine and reclaim their rightful jobs."