Why is the national security argument not convincing?

The national security argument is a justification provided for adopting protectionist policies such as tarriffs, quotas and other barriers by stating that it is unwise to become dependent on imports of certain products because it makes the nation vulnerable.

he National interest argument for protectionism mentions that Restricting imports is neither a wise decision nor solves problems, national interest arguments with respect to certain products states that for products like defense equipment, oil, technology, a country must not be too dependent on other countries.

it would be vulnerable to importing certain key products because if the nation becomes dependent on those key imported products, then it would be difficult to cut off.

A stockpile of resources would be the wiser decision, to use the foreign supplies when available, compared to preemptively restricting imports better to not depend on them.