Subject to the provisions of subsections (c) and (d) and notwithstanding any other provision of law, whenever a marketing order issued by the Secretary of Agriculture pursuant to section 608c of this title contains any terms or conditions regulating the grade, size, quality, or maturity of tomatoes, raisins, olives (other than Spanish-style green olives), prunes, avocados, mangoes, limes, grapefruit, green peppers, Irish potatoes, cucumbers, oranges, onions, walnuts, cherries, pecans, dates, filberts, table grapes, eggplants, kiwifruit, nectarines, clementines, plums, pistachios, apples, or caneberries (including raspberries, blackberries, and loganberries) produced in the United States the importation into the United States of any such commodity, other than dates for processing, during the period of time such order is in effect shall be prohibited unless it complies with the grade, size, quality, and maturity provisions of such order or comparable restrictions promulgated hereunder: Provided, That this prohibition shall not apply to such commodities when shipped into continental United States from the Commonwealth of Puerto Rico or any Territory or possession of the United States where this chapter has force and effect: Provided further, That whenever two or more such marketing orders regulating the same agricultural commodity produced in different areas of the United States are concurrently in effect, the importation into the United States of any such commodity, other than dates for processing, shall be prohibited unless it complies with the grade, size, quality, and maturity provisions of the order which, as determined by the Secretary of Agriculture, regulates the commodity produced in the area with which the imported commodity is in most direct competition. Such prohibition shall not become effective until after the giving of such notice as the Secretary of Agriculture determines reasonable, which shall not be less than three days. In determining the amount of notice that is reasonable in the case of tomatoes the Secretary of Agriculture shall give due consideration to the time required for their transportation and entry into the United States after picking. Whenever the Secretary of Agriculture finds that the application of the restrictions under a marketing order to an imported commodity is not practicable because of variations in characteristics between the domestic and imported commodity he shall establish with respect to the imported commodity, other than dates for processing, such grade, size, quality, and maturity restrictions by varieties, types, or other classifications as he finds will be equivalent or comparable to those imposed upon the domestic commodity under such order. The Secretary of Agriculture may promulgate such rules and regulations as he deems necessary, to carry out the provisions of this section. Any person who violates any provision if ^[1] this section or of any rule, regulation, or order promulgated hereunder shall be subject to a forfeiture in the amount prescribed in section 608a(5) of this title or, upon conviction, a penalty in the amount prescribed in section 608c(14) of this title, or to both such forfeiture and penalty.