Today's Trade Law Brain Teaser

I was recently asked whether Israel's large excise tax on automobiles, applied at the border, raises WTO law issues.  Israel has no domestic production of automobiles, so the tax de facto only applies to imports.  However, it is by definition non-discriminatory, because there is not domestic production to compare it with.  Nor does it seem to raise issues under Article XI, which specifically excludes taxes from its application.   If the measure were a product standard, it would be required to be the least trade restrictive measure under the TBT Agreement, regardless of domestic production.  But as a tax, it  appears subject to no similar proportionality requirement.  So, it seems that there is no legal problem.  What am I missing?