Current Leakage calculations regarding shock hazard. A complete picture?
Leakage currents are usually currents that are capacitively coupled to (for example) a chassis.  If a user could touch the chassis, AND the chassis is not grounded, then the potential on the chassis could cause a current to flow in the user and cause a shock.  Remember, two conductors separated by an insulator form a capacitor and it will conduct AC current according to I=C*dv/dt.

One example of this is the Y-capacitors used in power supplies for EMI filters.  Both sides of the line are connected through capacitors to chassis ground to filter the high frequency conducted EMI.  Now, if the ground prong on the AC cord is not connected (for whatever reason) the Y-Caps will cause the potential on the chassis to rise and you can feel a tingle if you get between the chassis and ground.

Regulatory requirements are such that the Y capacitors should not pass enough current to cause danger, but there are other potential paths for leakage currents as well.  A switching transistor mounted with an insulator to a grounded heatsink also capacitively couples currents into the chassis.

There's no violation of Kirchoff's current law in any of this.