Since his election to the Legislative Assembly of Alberta, Johnston has been involved with various committees. During his first term in office, he held the position of chair for the Social Care Facilities Review Committee, the Special Constable Review Committee, and the Alberta Heritage Savings Trust Fund Committee while also sitting as a member on a number of other committees. He also helped develop several bills including: "Correction Amendment Act, 2007, Safer Communities and Neighbourhoods Act, Peace Officer Act, and Traffic Safety Amendment Act, 2007".