Sherlock still stands by his original assessment. There are rules in place to protect him from people like Jim, and if Jim wanted him dead, he'd have done it already.

Whether or not there are rules about getting high around here, well... if there are, Sherlock was never made aware of them.

The second line is gone just as easily as the first, and any unpleasant sensations from snorting them are already being overpowered by everything else.