Employers considering a tolerant attitude towards recreational cannabis in the workplace should consider safety hazards and legal liabilities.  In the heyday of the two-martini lunch, employers regularly tolerated alcohol in the workplace or employees presumably impaired by alcohol returning to work.  Over the succeeding decades, employers began to concentrate on the business and legal liabilities imposed by drug and alcohol use and impairment in the workplace — including increased absenteeism, mistakes, sexual harassment, workplace violence,…