49 CFR §604.18

1. (a)An interested party may request an advisory opinion from the Chief Counsel only on matters involving specific factual events.
2. (b)A request for an advisory opinion shall be submitted in the following form:
3. (c)The Chief Counsel may request additional information, as necessary, from the party submitting the request for an advisory opinion.
4. (d)A request for an advisory opinion may be denied if:
   1. (1)The request contains incomplete information on which to base an informed advisory opinion;
   2. (2)The Chief Counsel concludes that an advisory opinion cannot reasonably be given on the matter involved;
   3. (3)The matter is adequately covered by a prior advisory opinion or a regulation; and
   4. (4)The Chief Counsel otherwise concludes that an advisory opinion would not be in the public interest.