According to the U.S. Occupational Safety and Health Administration (OSHA), machine guarding standards require provisions to protect against automatic restart for woodworking machinery, but not for some metalworking machinery (mechanical power presses being the exception).
While many tools used in metalworking do not have the same explicit requirement in the OSHA standards for protection against automatic restart, they (as with all electric equipment used in the workplace) are generally required to be listed and labeled by a Nationally Recognized Testing Laboratory (NRTL). These laboratories may have requirements addressing the issue of the prevention of automatic restarting in their listing and labeling criteria and testing protocols.
If there are such requirements, OSHA has a provision, found at 29 CFR 1910.303(b)(2), that "listed or labeled equipment shall be used or installed in accordance with any instructions included in the listing or labeling."
See Machine Guarding from OSHA for more information.