I think taking an excerpt from a report that was produced after everything was nutted out is misleading to say the least. The NTSB was highly critical of Sullys' decision to land on the Hudson and the initial simulator exercises lent weight to their argument after 7 of 13 attempts landed successfully at La Guardia, it was only after it was argued that there needed to be a 'startle' delay added to the simulations that it was proved that any attempt to return to land was not the right course. Now whilst the NTSB may have eventually said the simulations were unrealistic, who originally conducted the simulations to prove it could be done? They were also critical of why the double engine failure checklist was not completed.
Sully still had to defend himself before the NTSB that his actions were correct, there was no "oh you were PIC so everything you did was appropriate given it was an emergency", so no law covered him without test.