14 CFR 399.4: Nature and effect of policy statements.

Policy statements published in this part will be observed by the Department until rescinded, but any policy may be amended from time to time as experience or changing conditions may require. Changes in policy may be made with or without advance notice to the public and will become effective upon publication in the Federal Register unless otherwise provided. If it appears to the Department, in its consideration of any matter before it, that the application of a policy published in this part would run counter to an express provision of law or policy enunciated by Congress in 49 U.S.C., the published policy shall not be applicable to such matter.