Yes, no, sometimes. Though not specified in OSHA 29CFR1910.179, ASME B30.2 does require the use of hook latches in most cases, but it also offers some relief from the requirement. Specifically, the language within ASME states that "latch-equipped hooks shall used unless the application makes the use of the latch impractical or unnecessary".
Under OSHA regulations, hooks and chains must be visually inspected on a daily and monthly basis, with the monthly inspection recorded on a certificate form that includes the date of inspection, the signature of the person who performed the inspection and the serial number, or other identifier, of the hook or chain inspected.
According to ASME B30.10, hooks must be replaced when a) the hook has an increased throat opening exceeding 15% of the original design; or b) the hook is bent or twisted by more than 10 degrees; or c) the hook is worn more than 10% of the original dimension. Minor surfacecracks or gouges can be ground out as long as no more than 10% of the hook section is removed.
Generally speaking, no. Give the hook its last rites, discard it and replace it. Repairing hooks by welding and reshaping is not generally recommended by OSHA or ASME. If you do not like this answer, there is one reference to which you can turn. In an interpretation letter from OSHA, a specified procedure for repairing hooks was submitted and approved by OSHA (wewere shocked too when we found this!). We don't give any endorsement for this procedure, but if you're interested in seeing it, hit this link to the OSHA web site, then click on the interpretations button.