Sorry, I can see what you mean.
The short answer is yes and no.
UN Resolutions passed by the General Assembly are not binding.
UN Resolutions passed by the Security Assembly are deemed binding and can "authorize" the use of force; ie, the invasion or liberation of sovereign nations.
By becoming a member of the UN, you accept these conditions.
That's also why the six permanent members of the Security Council have so much power. They can veto any Security Council resolution. This is a shadow of post-WWII geo-politics. There is a movement in the UN to offer other major countries (such as Germany, India, China) permanent seats also. Not sure how far this will get, as it will devalue the current veto power the US and others enjoy.
Other things that also set International Law are signing an treaty or convention. Things such as the Geneva Convention, or the International Nuclear Test Ban Treaty. These are "law", but a country can withdraw from them; as the US has done with the INTBT.
Finally, there are agreements, protocols, conventions and treaties that can become international law once enough countries sign up. The Kyoto Protocol is a good example. Now that Russia has signed up and ratified the treaty, it has become law. The US ans Australia have not signed, but that is irrelevant as they can now be penalized by the so-called Kyoto Club until they change their behaviour or sign up. Whether that happens or not is debatable.
Mr Mephisto