For fresh eating, sure. But for re-canning it isn't recommended by the guidelines.

Re-canning already canned foods results in a sharp decline in the texture, consistency, and over-all quality. Plus there is sometimes the duplication of ingredients issue that causes problems. For example the salt or lemon juice added when first canned is then doubled in the second use recipe.

Add to that that we are talking salsa, which is a risky food to begin with since it is a low-acid mixture and is eaten fresh from the jar it is best to begin with fresh ingredients rather than adding ingredients that may have developed issues during shelf storage.

Of course you always have the option of ignoring the guidelines but the over-all quality of your salsa will be improved by using fresh ingredients and saving the canned ones - they store for years - for use in cooking recipes.

Dave