These days, when issues of justiciability or unilateralism arise, the security exception in Article XXI of GATT 1994 comes immediately to mind. However, these issues can arise in very different contexts, such as safeguards.
The Agreement on Safeguards exempts small suppliers of a product from developing Members from safeguard measures, but as throughout the WTO system it does not define developing Member. Most developing countries consider that developing status is based upon self-selection, and is thus not subject to dispute settlement, but this view certainly is not shared by the United States.
When the United States imposed safeguard measures on solar cells in January 2018, it exempted India as a small developing supplier. In May of this year, however, President Trump suspended India's status as a GSP beneficiary, on the grounds that India does not provide US exporters with fair access to its markets. In the same proclamation, the United States removed India from the list of developing Members benefiting from the small supplier exemption in respect to the solar cells safeguard (and to another safeguard measure on large residential washers).
It appears from the Proclamation that the United States now conflates GSP beneficiary status with developing Member status, and considers that India is no longer a developing country. Should India disagree, it could challenge the US decision in dispute settlement, and we would then learn whether the WTO DS system is prepared to rule whether or not a Member is a developing country.
From the US perspective, India might not be the ideal candidate for a test case. While the developing country status of Singapore, Korea or China may be debatable, India's GDP per capita is only slightly above $2000. That is by far the lowest among G20 countries, and is one thirtieth that of the United States and one fifth that of China.