The source is the article OP linked below the tweet.

The Supreme Court agreed to take the case after hearing from an unlikely coalition that spanned the political spectrum, including liberals such as California Gov. Gavin Newsom (D) and officials in Republican-led states such as Montana and Alabama. The officials described governments overwhelmed by the scale and complexity of homelessness. More than 600,000 people are homeless nationwide, according to federal data, and nearly half sleep outside.

Newsom — who leads the state with the country’s largest unhoused population and frequently criticizes the high court’s conservatives — welcomed the decision, saying it provides “definitive authority to implement and enforce policies to clear unsafe encampments from our streets.” This decision removes the legal ambiguities that have tied the hands of local officials for years and limited their ability to deliver on common-sense measures to protect the safety and well-being of our communities.”

Well he did have this to say about it so he certainly supports the decision:

Today’s ruling by the U.S. Supreme Court provides state and local officials the definitive authority to implement and enforce policies to clear unsafe encampments from our streets. This decision removes the legal ambiguities that have tied the hands of local officials for years and limited their ability to deliver on common-sense measures to protect the safety and well-being of our communities.

“California remains committed to respecting the dignity and fundamental human needs of all people and the state will continue to work with compassion to provide individuals experiencing homelessness with the resources they need to better their lives.”