Hadler participated on the Norwegian relay team together with Dagfinn Olsen, Ola Skarholt and Stig Berge, and won a bronze medal behind Sweden and Finland.

The relay was won by the Norwegian team, which consisted of Hadler and Ola Skarholt, Stig Berge and Per Fosser.

His wife Ingrid won gold medal in the individual course at the women's World Championships.

Med giftering, kart og kompass, as co-author along with his wife Ingrid Hadler.

[1] The 1972 World Orienteering Championships were held in Staré Splavy, Czechoslovakia, from 14 to 16 September.

[1] Hadler was appointed as a research worker at the institution Fondet for markeds- og distribusjonsforskning in 1971, and served as manager from 1976 to 1986.