For the Supreme Court to make rulings, there needs to be a lawsuit. Regardless, there was a ruling last year[0] that said the CDC didn't have the authority for a nationwide moratorium.
In addition, because this is LA doing this, not the federal government, the Supreme Court is less likely to take up an appeal should there be an actual lawsuit. They tend to prefer country/city lawsuits to stay in the state.
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[0]: Alabama Association of Realtors v. Department of Health and Human Services
https://www.cnn.com/2021/08/26/politics/supreme-court-ruling...
https://www.scotusblog.com/case-files/cases/alabama-associat...