A federal law could be passed, signed and enacted in 1 1/2 days to grant stated and/or FBI access in certain circumstances.
They can pass all the laws they want. It won't help them get into that phone. They can take the entire Constitution and just dump it into a shredder, and it won't help. The manufacturer can't even get into the phone. It would require a complete redesign of the processors, and still won't help them get into existing iPhones. Said iPhones would become much more valuable on the resale market if the government forced them to make all new phones crackable.