The "-law" suffix would probably apply to any tag on this site, so better not have it, I would say.
I actually prefer international-law.
The word "law" is not automatically appended to all of our tags. For example, we should still have criminal-law, corporate-law etc., where as we have tags for countries (e.g. united-states) and concepts (e.g. freedom-of-speech).
The two tags are different in meaning; at the very least, several of the questions there should not have the international-law tag, and others should.
As I understand it, international could be for questions about how things are handled around the world. This is possibly too broad for this site; questions like that should be narrowed, and the tag could be removed. On the other hand, international-law should be for questions about international law: treaties, conventions, the UN, and similar things, including maybe "which countries have jurisdiction in these cases". Only two of the international questions are about that (Which jurisdiction applies in a vessel? and Claiming my own country). Restrictions on international data storage? shouldn't have the international-law tag.
We should certainly not put treaties under international; that's not the term used to describe them. The "law" suffix doesn't apply to all tags by any stretch of the imagination, and even if it did we should use the phrase that someone would actually use instead of trying a this-site-specific contraction. For another example of where "-law" makes a massive difference, corporate-law covers a subset of what corporate might cover, because lots of stuff involving corporations isn't "corporate law".
I would say yes, international should be the tag we go with.