The Council of Trade Unions is investigating further legal action against former Pike River mine manager Peter Whittall.
Twenty-nine men were killed in explosions that began at the West Coast mine on 19 November 2010.
Twelve charges brought by the Ministry of Business, Innovation and Employment against Mr Whittall were dismissed by Judge Jane Farish in the Christchurch District Court in December last year.
CTU president Helen Kelly said on Tuesday why the charges against Mr Whittall were dropped needs further explanation that will decide whether a judicial review is needed.
Ms Kelly said victims' families support the CTU's move.