MSHA - Code of Federal Regulations - 30 CFR 56.14116
30 CFR § 56.14116
Hand-held power tools.
(a) Power drills, disc sanders, grinders and circular and chain saws,
when used in the hand-held mode shall be operated with controls which require
constant hand or finger pressure.
(b) Circular saws and chain saws shall not be equipped with devices
which lock-on the operating controls.