— This case involves the validity of a Tacoma business and occupation tax imposed upon the sale of scrap metal destined for the stream of foreign commerce. The City of Tacoma is appealing an adverse decision of the Pierce County Superior Court that the scrap metal was in the stream of foreign commerce and was, therefore, beyond the reach of municipal business and occupation tax.
Respondent General Metals of Tacoma, Inc. (hereinafter; “General Metals”) is engaged in the purchase and sale of scrap- metal with its principal place of business located on *561the Hylebos Waterway in Tacoma. In 1956, respondent General Metals Export Corp. (hereinafter: “Export Corp.”) was formed as a foreign sales affiliate of General Metals. Export Corp. has no office, but operates from that of General Metals. The two corporations have the same president and vice president/general manager. In the case of Export Corp., these two individuals are its only employees. As the same principals own the two respondent corporations, the relationship between the two entities is a so-called “brother-sister” affiliation, rather than that of a parent-subsidiary.
General Metals purchases quantities of scrap metal from various domestic sources. The purchased scrap is delivered to the General Metals facility on the Hylebos Waterway. A portion of the scrap is deposited upon the General Metals export pile to await export. The remainder of the scrap which requires processing is appropriately prepared by General Metals and then added to the export scrap pile. From time to time, General Metals may remove a portion of the export scrap for domestic sale, but this is infrequently done and amounts to less than 5 percent of scrap metal sales which are appropriately taxed.
Export Corp. solicits foreign orders for scrap metal primarily from Asian buyers. Shipment of scrap sold is made exclusively in foreign flag vessels. When the buyer’s vessel arrives dockside on the Hylebos Waterway in Tacoma, the ship is loaded with scrap by stevedores under contract with Export Corp. When loaded, the vessel issues the necessary documents accompanied by a letter of credit which Export Corp. negotiates for payment through its bank. Export Corp. is then invoiced by General Metals and Export Corp. makes payment to General Metals.
The interposition of Export Corp. between the foreign purchaser and General Metals has recently taken on a new dimension. Export Corp. has qualified as a Domestic International Sales Corporation (“DISC”) under the Revenue Act of 1971, tit. V, §§ 501-07, 85 Stat. 535 (codified in *562Scattered sections of 26 U.S.C.). The purpose of the DISC provisions is to stimulate export sales by deferring approximately one-half of the federal income taxes upon export profits. See generally Department of the Treasury, DISC: A Handbook for Exporters (1972). The DISC legislation clearly contemplates corporations similar to Export Corp. which exist solely to further the export sales of a single exporter. See Parsons, Some Thoughts on DISC, 9 Willamette L.J. 261 (1973); Hill & Repogle, The Wonderful World of DISC, 25 Okla. L. Rev. 381 (1972).
Appellant contends that the sale of scrap, metal by General Metals to Export Corp. is a wholesaling transaction subject to the Tacoma business and occupation tax. Contrarily, respondents assert that no taxable incident arises as the goods in question are irrevocably committed to the flow of foreign commerce before any transfer is accomplished, and, therefore, beyond the constitutional reach of state or municipal taxation. See U.S. Const, art 1, § 10, cl. 2.
It is a well settled constitutional doctrine that a state may not tax goods which have entered the stream of foreign commerce. See Brown v. Maryland, 25 U.S. (12 Wheat.) 419, 6 L. Ed. 678 (1827). In a case directly on point, Richfield Oil Corp. v. State Bd. of Equalization, 329 U.S. 69, 91 L. Ed. 80, 67 S. Ct. 156 (1946), the State of California sought to levy a sales tax upon the sale of oil bound for New Zealand. In this case, the oil was pumped from Richfield’s storage tanks at dockside into a waiting vessel. The United States Supreme Court reasoned that:
[W]hen the oil was pumped into the hold of the vessel, it passed into the control of a foreign purchaser and there was nothing equivocal in the transaction which created even a probability that the oil would be diverted to domestic use. . . . The means of shipment are unimportant so long as the certainty of the foreign destination is plain.
(Italics ours.) Richfield Oil Corp. v. State Bd. of Equalization, supra at 83. Thus, the shipment was held to be in the *563stream of foreign commerce and beyond the reach of state taxation.
The test applied to ascertain and determine whether goods have entered foreign commerce is one of reasonable facility and certainty. As stated in Empressa Siderurgica, S.A. v. Merced, 337 U.S. 154, 157, 93 L. Ed. 1276, 69 S.Ct. 995 (1949):
It is the entrance of the articles into the export stream that marks the start of the process of exportation. Then there is certainty that the goods are headed for their foreign destination and will not be diverted to domestic use. Nothing less will suffice.
The crucial test of entrance into the stream of foreign commerce has been very recently reaffirmed in Kosydar v. National Cash Register Co., 417 U.S. 62, 40 L. Ed. 2d 660, 94 S. Ct. 2108 (1974), in which the court noted there must be “actual movement” of the goods to remove them from the ambit of state taxation.
This court has long recognized the validity of the indicated test and the inherent legal principles prescribing the limits of state taxing authority. In Eardley Fisheries Co. v. Seattle, 50 Wn.2d 566, 314 P.2d 393 (1957), we acknowledged that the degree of certainty of export was determinative of the State’s ability to tax. See also Alaska S.S. Co. v. State, 31 Wn.2d 328, 196 P.2d 1001 (1948).
Applying the indicated test to the instant case, we find that the scrap metal in question was unequivocally committed to the stream of foreign commerce. In the instant case, as in Richfield, the transfer coincided with the loading of the commodity aboard ship. The vessels loaded by Export Corp. are controlled by a foreign purchaser, and forbidden by federal law from discharging their cargo at a domestic port. See Merchant Marine Act of 1920, 46 U.S.C. § 883. Thus, there is no chance that the scrap metal cargo would be diverted for domestic use, and as the scrap had been loaded before the taxable incident arose, it had begun its “actual movement” in the stream of export.
*564Aside from the constitutional limitations of the State’s power to tax, the City of Tacoma is bound by the explicit provisions of its own rules. Tacoma City Rule 177 (identical to WAC 458-20-193C) expressly provides in pertinent part:
Exports. A deduction is allowed with respect to export sales when as a necessary incident to the contract of sale the seller agrees to, and does deliver the goods (1) to the buyer at a foreign destination; or (2) to a carrier consigned to and for transportation to a foreign destination; or (3) to the buyer at shipside or aboard the buyer’s vessel or other vehicle of transportation under circumstances where it is clear the goods will be taken to a foreign destination.
In all circumstances there must be (a) a certainty of export and (b) the process of export must have started.
The clear intent of the quoted language is to exclude transactions such as those in the instant case. Additionally, we find instructive the interpretation of the State version of rule 177, WAC 458-20-193C, rendered by the Department of Revenue in ETB 448.04.193C relating to the tax treatment of DISC’S under WAC 458-20-193C. The Department of Revenue excludes from State business and occupation taxation export transactions between a DISC (Export Corp.) and its affiliated supplier (General Metals). Hence, the transaction in question is not taxable under WAC 458-20-193C which is virtually identical to Tacoma’s rule 177.
We must conclude, therefore, that not only is the export sale of scrap metal beyond the constitutional reach of Tacoma’s taxing power, but also the transaction in question is not taxable under Tacoma’s own rule. The judgment of the Superior Court should be affirmed. It is so ordered.
Stafford, Wright, Utter, and Brachtenbach, JJ., concur.