While playing at club level, Lacey also worked for Allied Irish Banks and as sales representative for the East Cork Oil Company before becoming a coach development officer for Munster Rugby in 1999.

[14] On 8 October 2010 Lacey made his debut as a Heineken Cup referee when he took charge of a 2010–11 pool stage game between Northampton Saints and Castres Olympique.

[2][19] Lacey subsequently took charge of pool stage matches and semi-finals at both the 2010 and 2011 IRB Junior World Championships.

[6] On 1 February 2014 Lacey made his debut as a Six Nations Championship referee when he took charge of a match between Wales and Italy at the Millennium Stadium.

[5] On 16 August 2014 Lacey made his debut as a Rugby Championship referee when he took charge of a match between South Africa and Argentina at the Loftus Versfeld Stadium.

[22][23] Lacey also served as a referee at the 2015 Rugby World Cup and took charge of the bronze final between South Africa and Argentina.

[24][3][13][25] In October 2017, together with Andrew Brace, George Clancy and Joy Neville, Lacey was one of seven referees offered professional contracts by the IRFU.