They did take some protectionist measures with regard to long distance trade. I'll quote a couple of relevant sections of Klaas Veenhof's Mesopotamia: The Old Assyrian Period.

>The quantitative relation between the expensive "Akkadian textiles", imported from the south, and the institutional or domestic textile production in Assur... is still not clear, but the importance of the textile trade for Assur is underlined by evidence for clearly protectionist measures of the City Assembly, contained in the letters VS 26, 9 and AKT 3, 73:9ff., studied in Veenhof 2003d, 89ff. The first forbids trade in specific types of Anatolian textiles and the second probably obliges traders to buy more textiles, by limiting the quantity of tin that could be bought with the silver arriving from Assur.

p. 83

>But import of textiles and presumably copper from the south apparently did not prevent considering "Akkadians'' as rivals in the trade. This is implied by the just mentioned prohibition of selling gold to them and confirmed by a surprising stipulation in the draft of a treaty with a ruler in southern Anatolia, probably somewhere in the area of the great western bend of the Euphrates, near Hahhum. He has to promise that he will extradite Akkadians, presumably Babylonian traders who travelled north via the Euphrates and came to his country, to be killed by the Assyrians. But alongside such protectionism also good relations were necessary with cities and lands whose cooperation was essential for the trade and the safety of the caravans.

p. 98