You can only really judge Kirk's action based on the PD as it existed in that era, comparrisons with the PD as it stood in Picard's era are unfair.
After all lmany laws they evolve over time, new cavets are added due to unforseen circumstances having arisen and being resolved. So what was within the law in 2267 might not be within the law in 2367. Training during the Academy days would have reflected this change within in Starfleet and as such they would have been taught what was within the rules and what wasn't.
Agreed, these were very different times.