The Government of Canada, through the Department of Justice, should institute a study of the accountability of corporate executives and directors for the wrongful or negligent acts of the corporation and should introduce in the Parliament of Canada such amendments to legislation as are necessary to ensure that corporate executives and directors are held properly accountable for workplace safety.
If there was no legislation in place then senior employees could not be trusted to ensure workplace safety
The context states that legislation is needed, so it must be needed because corporate executives and directors (aka senior employees) can't be trusted to safeguard safety. The system could likely not understand the use of 'senior employees' in place of corporate executives and directors. 