The states have limited power to defy the feds.

Case in point: legalized marijuana. That said, my fear in regards to states defying laws is:

• Targeted attacks by MAGA terrorists, particularly regarding anything LGBTQ+ or reproductive healthcare related.
• The fed withholding federal funds to punish states that don’t fall in line.

The former is particularly concerning as police and the national guard are predominately right-wing. My state passed the SAFE-T Act to address abuses in the police/justice system. Naturally, various police departments weren’t happy about this, and through obtuse interpretation of the act they’ll claim they can’t legally do vital parts of their job – something I’ve seen multiple times first hand. Refusing to do their job competently in response to MAGA terrorism isn’t hard to imagine.

The later gets tricky. Most of the states that would push back against unjust federal laws are also states that pay more in federal taxes than they receive in aid. The “obvious” solution withhold federal tax dollars to make up the difference … which would be next to impossible in practice. Even if states mange to do it they’d be playing into Republican hands by defunding essential federal services.