Originally Posted by WEACLRS

The FAA is busting MEI's for this. The regulation is 14 CFR Part 61.193 Flight instructor privileges:

"A person who holds a flight instructor certificate is authorized within the limitations of that person's flight instructor certificate and ratings to give training and endorsements that are required for, and relate to:

(a) A student pilot certificate;
(b) A pilot certificate;
(c) A flight instructor certificate;
(d) A ground instructor certificate;
(e) An aircraft rating;
(f) An instrument rating;
(g) A flight review, operating privilege, or recency of experience requirement of this part;
(h) A practical test; and
(i) A knowledge test."

If you can't demonstrate the instruction you are giving falls into one of these areas, then you can't act as a CFI and therefore can not log pilot-in-command time as a CFI.