According to the Associated Press, a federal judge sided with the National Labor Relations Board last August, requiring Massey to offer jobs to 85 individuals furloughed when the former owner of the Cannelton mine, Horizon Natural Resources, entered bankruptcy.
Massey later reopened the operation as a non-union mine under its Mammoth Resources subsidiary.
The news service said that 51 members of the group accepted the offer to return, according to documentation filed recently by the judge.
While Massey had initially requested a stay of the order pending its appeal, it withdrew the application after opening a new operation and altered work schedules there so that the extras workers could be accommodated, the AP said.
Neither Massey nor the UMWA had released a public statement on the move as of press time.
Last November, Judge Paul Boggs said Massey made the decision to avoid UMWA regulations and proceed with contract negotiations for the mine, which had been union-operated since about the 1970s.
However, Massey said at the time 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.
The judge rejected the operator's stance last year, arguing that the mine was run in the same manner and there was evidence Massey wanted to discourage union activity and UMWA bargaining.
Massey said in a statement after the decision that it disagreed and would challenge it.