I remember reading in the code that it is required to use a tapped Screw or a nut and bolt as a means to connect a bond to a metal building or beam. I have a situation where someone has used a Self tapping screw (tek-screw) to fasten a bonding jummper to from one metal structure to another.. what is the Code that says this isn't allowed. Thank you for your time.

At the beginning of Article 250 is the following, see #5:

250.8 Connection of Grounding and Bonding Equipment.

(A) Permitted Methods. Grounding conductors and bonding jumpers shall be connected by one of the following means:
(1) Listed pressure connectors
(2) Terminal bars
(3) Pressure connectors listed as grounding and bonding equipment
(4) Exothermic welding process
(5) Machine screw-type fasteners that engage not less than two threads or are secured with a nut.
(6) Thread-forming machine screws that engage not less than two threads in the enclosure.
(7) Connections that are part of a listed assembly
(8) Other listed means