National Grid trusts the general public this much?
Originally Posted by AllanJ
Yes, disconnecting the building system from the power company lines during use of a generator is mandatory and within code. But the NEC requires more than that, specifically a means such as a transfer switch that prevents inadvertently reconnecting the building system to the power company lines while still energized by the generator.
Now the NEC does permit interlocks such as cams or levers that immobilize switch handles but which are not foolproof for example if the front cover of the panel together with such interlocks is removed.