Final answer:
Since the mid-1990s, the Supreme Court has trended towards limiting the power of the national government over state governments. This is evident in decisions like Uniteds on state law enforcement and Medicaid expansion.
Step-by-step explanation:
The best description of the Supreme Court's trend in interpreting federalism since the mid-1990s is that the Court has limited the power of the national government over the state governments.
This trend is demonstrated in cases such as United States v. Lopez (1995), where the Court struck down a federal law on the basis that it did not substantially affect interstate commerce, thereby indicating a more narrow interpretation of the Commerce Clause and a limitation on federal power in relation to state authority.
In addition, the Supreme Court has, in certain cases, supported state powers over the federal government. For instance, in 1997, the Court ruled against a federal law mandating state and local law enforcement.
To conduct background checks for gun purchases, and in 2012, the court decided that the federal government couldn't force states to expand Medicaid. These decisions contribute to the trend of reaffirming state power over certain aspects of governance, as opposed to the broader federal power seen in earlier decades.