BACKGROUND
School staff members' consistent enforcement of school tobacco policies (STPs) is needed to decrease adolescent smoking and exposure to tobacco smoke. Staff's confidence, indicating their perceived ability to cope with students' negative responses, explains variations in staff's STPs enforcement, yet understanding of the determinants for confidence is lacking. We analyzed the conditions in which the staff feel confident in addressing students who violate STPs to support staff's enforcement. 

METHODS: Data consists of 81 semi-structured interviews with the staff members from 26 secondary schools in seven European cities in Belgium, Finland, Germany, Ireland, Italy, The Netherlands, and Portugal. In every city, 3-4 staff members (senior management, teachers, supportive staff) in 3-4 schools (academic-vocational, high-low SES area) were interviewed. Transcripts were analyzed with thematic analysis.

RESULTS
When staff felt confident in their ability to prevent, diminish, or handle students' negative responses, they were more likely to address students on STP violations. The staff was more confident (1) when consistent policy enforcement within school and regarding the wider society ensured staff legitimacy for STPs enforcement, (2) when dialog and mutual familiarity with students allowed the staff to facilitate constructive interaction with STP violators, and (3) when organizational backup structures provided staff collegial support to overcome challenges in the enforcement. These conditions would support consistent enforcement, especially with persistent misbehavers and among the more uncertain staff members.

CONCLUSIONS
Our study stresses the need to implement strategies at multiple levels to strengthen staff's confidence for STP enforcement. To support staff's legitimacy for enforcement, we suggest reinforcing structures and practices that facilitate consistency in STP enforcement; to support staff's ability for constructive interaction with STP violators, we suggest strengthening staff's social and emotional learning; and to support staff's experience of collegial support, we suggest reinforcing staff's collective ability to cope with students' negative responses.